Soil pollution monitoring device

Abstract

The invention is applied to the technical field of soil monitoring, and discloses a soil pollution monitoring device which comprises a rack, a mounting cylinder is fixedly arranged on the outer surface of the rack, a lifting detection mechanism is arranged in the mounting cylinder, and a sample can be completely taken out without pollution in a mode of sampling and sealing after drilling into the ground. According to the soil pollution monitoring device, the lifting detection mechanism is arranged, a rotating motor drives a center disc, a connecting rod, a center column, a drill bit and other components to operate, the drill bit can be drilled into the ground, and the drilling depth can be controlled through a first electric push rod and a lower push rod; compared with a traditional mode which depends on manual operation for sampling and is difficult to ensure the accuracy of the sampling depth, the device can accurately reach the specified depth for sampling, the problem that the sampling depths are uneven due to manual operation differences is effectively solved, and the sampled sample can accurately reflect the pollution condition of a specific soil layer.

Description

Technical Field

[0001] The present invention relates to the technical field of soil monitoring, and in particular to a soil pollution monitoring device. Background Art

[0002] In today's era, with the rapid advancement of industrialization and urbanization, soil pollution has become a serious global environmental problem, which poses an unprecedented threat to ecological balance, sustainable agricultural development and human life and health. As the foundation for the growth of all things, once soil is polluted, it will not only lead to reduced crop yields and quality, but also cause harmful substances to enter the human body through the food chain, causing various diseases. Therefore, it is urgent to carry out accurate and efficient soil pollution monitoring;

[0003] The traditional soil pollution monitoring process relies heavily on manual sampling, and then the samples are transferred to the laboratory for detailed analysis. However, this process has many drawbacks. During the sampling stage, it is difficult to ensure the accuracy of the sampling depth through manual operation. The different techniques of different operators can easily cause uneven sampling depths, making it impossible for the samples to accurately reflect the pollution status of a specific soil layer. Moreover, after the samples are collected, due to the lack of effective immediate sealing measures, they are easily mixed with external impurities, such as dust and microorganisms in the air, and other foreign matter in the surrounding environment. This will undoubtedly seriously interfere with the subsequent test data, causing deviations in the analysis results and making it difficult to truly present the degree of soil pollution. Summary of the invention

[0004] The purpose of the present invention is to provide a soil pollution monitoring device to solve the problems in the traditional soil pollution monitoring process proposed in the above background technology that the sampling depth accuracy is difficult to ensure and the sample is easily mixed with external impurities that interfere with the detection data.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a soil pollution monitoring device, comprising a frame, a mounting cylinder is fixedly arranged on the outer surface of the frame, and a rotating top cover is installed on the upper end of the mounting cylinder, a switching motor is fixedly arranged on the inner top surface of the top cover, and a switching gear is fixedly connected to the lower end of the output shaft of the switching motor, a linkage gear block is fixedly arranged on the inner side surface of the upper end of the mounting cylinder, a first electric push rod is fixedly arranged on the inner top surface of the top cover, and the lower end of the first electric push rod is fixedly connected to the lower end of a lower push rod, the upper end of the lower push rod passes through the inner surface of the mounting cylinder, and a clearance groove is opened on the inner surface of the mounting cylinder, a lifting detection mechanism is arranged inside the mounting cylinder, and the sample can be taken out intact and uncontaminated by drilling into the ground for sampling and sealing;

[0006] The lifting detection mechanism comprises: a lifting plate, the lifting plate is slidably mounted on the inner surface of the mounting cylinder, and a rotary motor is fixedly mounted on the upper surface of the lifting plate, and a center disk is fixedly connected to the lower end of the output shaft of the rotary motor, a connecting rod is fixedly arranged on the lower surface of the center disk, a center column is fixedly connected to the lower end of the connecting rod, and a drill bit is installed at the lower end of the center column, a mounting disk is installed at the upper end of the center column, and a spiral plate is fixedly arranged on the lower surface of the mounting disk, a second electric push rod is fixedly mounted on the outer surface of the lower end of the connecting rod, and a connecting frame is fixedly connected to the lower end of the second electric push rod, and a rotary sampling mechanism is arranged on the surface of the center column, and the purpose of sampling at a specified depth is achieved by rotating the sampling.

[0007] The rotary cutting sampling mechanism includes: a ventilation rod, which is rotatably installed inside the side surface of the central column, and the upper end of the ventilation rod passes through the upper surface of the central column, and a functional gear is fixedly arranged on the outer surface of the upper end of the ventilation rod, a sampling motor is fixedly installed on the upper surface of the central column, and the lower end of the output shaft of the sampling motor is fixedly connected to the sampling gear, a pressure chamber is opened inside the lower end of the central column, and a piston plate is arranged on the inner side of the pressure chamber, and a connecting groove is opened on the inner surface of the lower end of the pressure chamber, a sampling plate is arranged inside the lower end of the central column, and a storage chamber is opened inside the central column below the sampling plate.

[0008] Preferably, the switching gear is meshed with the mounting cylinder through a linkage gear block, one end of the lower push rod passing through the inner surface of the mounting cylinder is flush with the give way groove, and one end of the lower push rod passing through the inner surface of the mounting cylinder overlaps with the vertical projection of the lifting plate.

[0009] The above technical solution can ensure that when the switching motor drives the switching gear to rotate, the top cover can reliably rotate stably relative to the mounting tube through engagement with the linkage gear block, changing the angle of the top cover and other states.

[0010] Preferably, a spring is connected between the lifting plate and the mounting tube, and the lifting plate is rotatably connected to the center disk, the center column, drill bit, mounting disk and spiral plate are concentrically arranged, and the inner surface of the spiral plate fits with the outer surface of the center column, and the lower end of the spiral plate fits with the upper end of the drill bit, and the center column and the drill bit are threadedly connected.

[0011] By adopting the above technical solution, the connection of the spring enables the lifting plate to have a certain buffering capacity when sliding in the installation tube, and can assist its reset when it is not subjected to external force or the external force disappears, thereby ensuring the stability and reliability of the device operation.

[0012] Preferably, the lower end of the second electric push rod is slidably connected to the central column, and the connecting frame is mounted in a snap-fitting manner with the mounting plate.

[0013] By adopting the above technical solution, the engaging installation design of the connecting frame and the mounting plate allows the second electric push rod to accurately drive the mounting plate to move up and down through the connecting frame when receiving a control signal to perform a telescopic action.

[0014] Preferably, the ventilation rod is of hollow design, and the lower end of the ventilation rod is connected to the pressure chamber through a connecting groove, and the ventilation rod is connected to the center column by sliding friction.

[0015] By adopting the above technical solution, the hollow design of the ventilation rod and the structure connected to the pressure chamber through the connecting groove make it possible to transport gas to the pressure chamber through the ventilation rod or to achieve operations such as sucking out the gas in the pressure chamber.

[0016] Preferably, the functional gear and the sampling gear are concentrically arranged, and the functional gear and the ventilation rod are concentrically designed.

[0017] The adoption of the above technical solution ensures that when the sampling motor drives the sampling gear to rotate, power can be accurately and stably transmitted to the functional gear, thereby driving the ventilation rod concentric therewith to rotate accordingly.

[0018] Preferably, the pressure chamber and the piston plate are connected by sliding friction, and the upper end of the piston plate is flush with the upper end of the sampling plate.

[0019] By adopting the above technical solution, the pressure chamber and the piston plate are connected by sliding friction, so that when the air pressure in the pressure chamber changes, the piston plate can slide smoothly along the inner wall of the pressure chamber under the action of pressure.

[0020] Preferably, the sampling plate is designed to be arc-shaped, and the outer surface of the sampling plate is in contact with the inner surface of the piston plate.

[0021] By adopting the above technical solution, when the sampling plate is not rotating, it will not affect the normal lifting and lowering of the piston plate under the action of air pressure.

[0022] Preferably, the sampling plate and the central column are eccentrically designed, and the minimum distance between the two ends of the sampling plate is greater than the distance from the center of the ventilation rod to the outer edge of the spiral plate.

[0023] By adopting the above technical solution, the soil on the inner wall of the hole drilled by the drill bit and the spiral plate can be scraped and collected when the sampling plate rotates.

[0024] Compared with the prior art, the beneficial effects of the present invention are: the soil pollution monitoring device:

[0025] 1. A lifting detection mechanism is set up, which drives the center plate, connecting rod, center column and drill bit and other components to operate through the rotary motor, so that the drill bit can be drilled into the ground, and the drilling depth can be controlled by the first electric push rod and the lower push rod. Compared with the traditional method of relying on manual sampling and difficult to ensure the accuracy of sampling depth, this device can accurately reach the specified depth for sampling, effectively solving the problem of uneven sampling depth caused by differences in manual operation, so that the samples taken can accurately reflect the pollution status of a specific soil layer;

[0026] 2. Furthermore, the rotary cutting sampling mechanism in the device cooperates with the ventilation rod, sampling motor, piston plate, sampling plate and storage chamber and other components. After obtaining the sample at the specified depth by rotating the sampling method, the sample can be immediately sealed in the storage chamber, so as to avoid the situation where the sample is easily mixed with external impurities due to the lack of effective and immediate sealing measures after collection as in the traditional method, thereby reducing the interference with subsequent detection data and more realistically presenting the degree of soil pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the present invention;

[0028] Figure 2 It is a schematic diagram of the three-dimensional structure of the connection between the frame, the mounting tube and the top cover of the present invention;

[0029] Figure 3 It is a schematic diagram of the three-dimensional structure of the overall cutaway surface of the present invention;

[0030] Figure 4 This is a schematic diagram of the three-dimensional structure of the switching motor, the switching gear and the linkage gear block of the present invention;

[0031] Figure 5 This is a schematic diagram of a three-dimensional structure of a connecting rod, a center column and a drill bit connected in the present invention;

[0032] Figure 6 This is a schematic diagram of the three-dimensional structure of the functional gear, sampling motor and sampling gear connected in the present invention;

[0033] Figure 7 It is a three-dimensional structural schematic diagram of the cross-section surface connecting the central column and the ventilation rod of the present invention;

[0034] Figure 8 This is a schematic diagram of the three-dimensional structure of the connection between the center column and the piston plate of the present invention;

[0035] Fig. 9 It is a three-dimensional structural schematic diagram of the cross-section surface of the pressure chamber, the piston plate and the connecting groove of the present invention;

[0036] Fig.10 It is a three-dimensional structural schematic diagram of the ventilation rod and the sampling plate in the working state of connection of the present invention.

[0037] In the figure: 1. frame; 2. mounting cylinder; 3. top cover; 4. switching motor; 5. switching gear; 6. linkage gear block; 7. first electric push rod; 8. lower push rod; 9. clearance groove; 10. lifting plate; 11. rotation motor; 12. center plate; 13. connecting rod; 14. center column; 15. drill bit; 16. mounting plate; 17. spiral plate; 18. second electric push rod; 19. connecting frame; 20. ventilation rod; 21. functional gear; 22. sampling motor; 23. sampling gear; 24. pressure chamber; 25. piston plate; 26. connecting groove; 27. sampling plate; 28. storage chamber. DETAILED DESCRIPTION

[0038] 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0039] See also Figure 1-Figure 10 , the present invention provides a technical solution: a soil pollution monitoring device.

[0040] Embodiment 1: This embodiment discloses a frame 1, a mounting cylinder 2 is fixedly provided on the outer surface of the frame 1, and a rotating top cover 3 is installed on the upper end of the mounting cylinder 2, a switching motor 4 is fixedly provided on the inner top surface of the top cover 3, and a switching gear 5 is fixedly connected to the lower end of the output shaft of the switching motor 4, a linkage gear block 6 is fixedly provided on the inner side surface of the upper end of the mounting cylinder 2, a first electric push rod 7 is fixedly provided on the inner top surface of the top cover 3, and the lower end of the first electric push rod 7 is fixedly connected to the lower end of a lower push rod 8, the upper end of the lower push rod 8 passes through the inner surface of the mounting cylinder 2, and a clearance groove 9 is provided on the inner surface of the mounting cylinder 2, a lifting and lowering detection mechanism is provided inside the mounting cylinder 2, and the sample can be taken out intact and uncontaminated by drilling into the ground for sampling and sealing;

[0041] The lifting detection mechanism includes: a lifting plate 10, the lifting plate 10 is slidably mounted on the inner surface of the mounting tube 2, and a rotation motor 11 is fixedly mounted on the upper surface of the lifting plate 10, and a center disk 12 is fixedly connected to the lower end of the output shaft of the rotation motor 11, a connecting rod 13 is fixedly arranged on the lower surface of the center disk 12, a center column 14 is fixedly connected to the lower end of the connecting rod 13, and a drill bit 15 is installed at the lower end of the center column 14, a mounting plate 16 is installed on the upper end of the center column 14, and a spiral plate 17 is fixedly arranged on the lower surface of the mounting plate 16, a second electric push rod 18 is fixedly mounted on the outer surface of the lower end of the connecting rod 13, and a connecting frame 19 is fixedly connected to the lower end of the second electric push rod 18;

[0042] The switching gear 5 is meshed and connected with the mounting cylinder 2 through the linkage gear block 6, and one end of the lower push rod 8 that passes through the inner surface of the mounting cylinder 2 is flush with the clearance groove 9, and one end of the lower push rod 8 that passes through the inner surface of the mounting cylinder 2 overlaps with the vertical projection of the lifting plate 10;

[0043] A spring is connected between the lifting plate 10 and the mounting tube 2, and the lifting plate 10 is rotatably connected to the center disk 12. The center column 14, the drill bit 15, the mounting disk 16 and the spiral plate 17 are concentrically arranged, and the inner surface of the spiral plate 17 fits with the outer surface of the center column 14, and the lower end of the spiral plate 17 fits with the upper end of the drill bit 15. The center column 14 and the drill bit 15 are threadedly connected;

[0044] The lower end of the second electric push rod 18 is slidably connected to the central column 14, and the connecting frame 19 is engaged and installed with the mounting plate 16;

[0045] When in use, first push the installation tube 2 to the specified position through the frame 1, then start the switching motor 4 under the top cover 3, the switching motor 4 drives the switching gear 5 to rotate, and the switching gear 5 makes the top cover 3 rotate at the upper end of the installation tube 2 by meshing with the linkage gear block 6. During the process, the first electric push rod 7 drives the upper end of the lower push rod 8 to rotate in the give way groove 9 as the top cover 3 rotates, until the upper end of the lower push rod 8 rotates to the lifting plate 10 just above the soil to be sampled, at this time start the first electric push rod 7 and the rotation motor 11, the first electric push rod 7 squeezes the upper surface of the lifting plate 10 through the lower push rod 8 so that the lifting plate 10 slides down and compresses the spring between the installation tube 2, and the rotation motor 11 drives the center column 14 and the drill bit 15 to rotate through the center disk 12 and the connecting rod 13, and the drill bit 15 digs downward by rotating during the downward movement;

[0046] During the process, the mounting disk 16 keeps synchronous rotation with the center column 14 through the connecting frame 19. At this time, the spiral plate 17 rotates synchronously with the mounting disk 16 to gradually transport the soil upward until the drill bit 15 reaches a predetermined depth. When sampling is required, the second electric push rod 18 is started. The second electric push rod 18 drives the mounting disk 16 and the spiral plate 17 to move upward through the connecting frame 19, so that the upward movement of the lower end of the spiral plate 17 does not block the subsequent sampling operation.

[0047] Embodiment 2: Based on Embodiment 1, this embodiment discloses that a rotary cutting sampling mechanism is provided on the surface of the central column 14, and the purpose of sampling at a specified depth is achieved by rotating the sample outward;

[0048] The rotary cutting sampling mechanism includes: a ventilation rod 20, the ventilation rod 20 is rotatably mounted inside the side surface of the central column 14, and the upper end of the ventilation rod 20 passes through the upper surface of the central column 14, and a functional gear 21 is fixedly arranged on the outer surface of the upper end of the ventilation rod 20, a sampling motor 22 is fixedly mounted on the upper surface of the central column 14, and a sampling gear 23 is fixedly connected to the lower end of the output shaft of the sampling motor 22, a pressure chamber 24 is opened inside the lower end of the central column 14, and a piston plate 25 is arranged on the inner side of the pressure chamber 24, and a connecting groove 26 is opened on the inner surface of the lower end of the pressure chamber 24, a sampling plate 27 is arranged inside the lower end of the central column 14, and a storage chamber 28 is opened inside the central column 14 below the sampling plate 27;

[0049] The ventilation rod 20 is hollow in design, and the lower end of the ventilation rod 20 is connected to the pressure chamber 24 through the connecting groove 26, and the ventilation rod 20 is connected to the central column 14 by sliding friction;

[0050] The function gear 21 and the sampling gear 23 are concentrically arranged, and the function gear 21 and the ventilation rod 20 are concentrically designed;

[0051] The pressure chamber 24 and the piston plate 25 are connected by sliding friction, and the upper end of the piston plate 25 is flush with the upper end of the sampling plate 27;

[0052] The sampling plate 27 is designed to be arc-shaped, and the outer surface of the sampling plate 27 is in contact with the inner surface of the piston plate 25;

[0053] The sampling plate 27 and the central column 14 are eccentrically designed, and the minimum distance between the two ends of the sampling plate 27 is greater than the distance from the center of the ventilation rod 20 to the outer edge of the spiral plate 17;

[0054] Before sampling, one end of a hose is connected to the upper end of the ventilation rod 20, and the other end of the hose is connected to a pressure device to facilitate air extraction and air injection. When the drill bit 15 reaches the specified depth and the spiral plate 17 moves up, the pressure device is started to extract air from the inside of the ventilation rod 20 through the hose. At this time, the ventilation rod 20 extracts air from the inside of the pressure chamber 24 through the connecting groove 26, so that the piston plate 25 slides down and retracts into the pressure chamber 24. At this time, the sampling motor 22 is started. The sampling motor 22 is driven by the meshing of the sampling gear 23 and the functional gear 21. The ventilation rod 20 rotates to drive the sampling plate 27 to rotate. During the rotation of the sampling plate 27, the soil on the inner wall of the hole outside the outer edge of the spiral plate 17 is scraped and sampled. As the spiral plate 17 rotates, the soil scraped off the inner wall of the hole moves along with the sampling. The rotation of the sample plate 27 is driven into the storage chamber 28 until the sampling plate 27 rotates one circle and resets. At this time, the pressure equipment is started to inject air into the ventilation rod 20 through the hose. At this time, the ventilation rod 20 injects air into the pressure chamber 24 through the connecting groove 26, so that the piston plate 25 slides up and extends out of the pressure chamber 24 to close the storage chamber 28, thereby preventing the sample from being contaminated during the upward recovery process of the drill bit 15. After the sampling is completed, the first electric push rod 7 drives the lower push rod 8 to move up and reset, and the lifting plate 10 drives the drill bit 15 to move up and reset under the support of the spring between the lifting plate 10 and the mounting tube 2. At this time, the drill bit 15 is twisted to make the drill bit 15 disengage from the threaded connection with the center column 14. At this time, the sample in the storage chamber 28 can be directly poured out to facilitate the collection of the sample.

[0055] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A soil pollution monitoring device, comprising a frame (1), a mounting tube (2) fixedly arranged on the outer surface of the frame (1), and a rotatable top cover (3) installed on the upper end of the mounting tube (2), a switching motor (4) fixedly arranged on the inner top surface of the top cover (3), and a switching gear (5) fixedly connected to the lower end of the output shaft of the switching motor (4), a linkage gear block (6) fixedly arranged on the inner side surface of the upper end of the mounting tube (2), a first electric push rod (7) fixedly arranged on the inner top surface of the top cover (3), and the lower end of the first electric push rod (7) fixedly connected to the lower end of a lower push rod (8), the upper end of the lower push rod (8) passes through the inner side surface of the mounting tube (2), and a clearance groove (9) is provided on the inner side surface of the mounting tube (2), characterized in that: The installation cylinder (2) is provided with a lifting detection mechanism inside, and the sample is taken out intact and uncontaminated by drilling into the ground and sealing the sample. The lifting detection mechanism comprises: a lifting plate (10), the lifting plate (10) is slidably mounted on the inner surface of the mounting tube (2), and a rotation motor (11) is fixedly mounted on the upper surface of the lifting plate (10), and the lower end of the output shaft of the rotation motor (11) is fixedly connected to a center disk (12), a connecting rod (13) is fixedly arranged on the lower surface of the center disk (12), the lower end of the connecting rod (13) is fixedly connected to a center column (14), and the lower end of the center column (14) is installed A drill bit (15) is provided, a mounting plate (16) is installed at the upper end of the center column (14), and a spiral plate (17) is fixedly provided on the lower surface of the mounting plate (16), a second electric push rod (18) is fixedly installed on the outer surface of the lower end of the connecting rod (13), and a connecting frame (19) is fixedly connected to the lower end of the second electric push rod (18), and a rotary cutting sampling mechanism is provided on the surface of the center column (14), and the purpose of sampling at a specified depth is achieved by rotating the sampling.

2. A soil pollution monitoring device according to claim 1, characterized in that: The rotary cutting sampling mechanism comprises: a ventilation rod (20), wherein the ventilation rod (20) is rotatably mounted inside the side surface of the central column (14), and the upper end of the ventilation rod (20) penetrates the upper surface of the central column (14), and a functional gear (21) is fixedly arranged on the outer surface of the upper end of the ventilation rod (20); a sampling motor (22) is fixedly mounted on the upper surface of the central column (14), and the lower end of the output shaft of the sampling motor (22) is fixedly connected to a sampling gear (23); a pressure chamber (24) is provided inside the lower end of the central column (14), and a piston plate (25) is provided inside the pressure chamber (24), and a connecting groove (26) is provided on the inner surface of the lower end of the pressure chamber (24); a sampling plate (27) is provided inside the lower end of the central column (14), and a material storage chamber (28) is provided inside the central column (14) below the sampling plate (27).

3. A soil pollution monitoring device according to claim 1, characterized in that: The switching gear (5) is meshedly connected with the mounting tube (2) through a linkage tooth block (6); one end of the lower push rod (8) passing through the inner surface of the mounting tube (2) is flush with the clearance groove (9); and one end of the lower push rod (8) passing through the inner surface of the mounting tube (2) partially overlaps with the vertical projection of the lifting plate (10).

4. A soil pollution monitoring device according to claim 1, characterized in that: A spring is connected between the lifting plate (10) and the mounting tube (2), and the lifting plate (10) is rotatably connected to the center disk (12). The center column (14), the drill bit (15), the mounting disk (16) and the spiral plate (17) are concentrically arranged, and the inner surface of the spiral plate (17) is in contact with the outer surface of the center column (14), and the lower end of the spiral plate (17) is in contact with the upper end of the drill bit (15). The center column (14) and the drill bit (15) are threadedly connected.

5. A soil pollution monitoring device according to claim 1, characterized in that: The lower end of the second electric push rod (18) is slidably connected to the central column (14), and the connecting frame (19) is mounted in a snap-fitting manner on the mounting plate (16).

6. A soil pollution monitoring device according to claim 2, characterized in that: The ventilation rod (20) is of hollow design, and the lower end of the ventilation rod (20) is connected to the pressure chamber (24) through a connecting groove (26), and the ventilation rod (20) and the central column (14) are connected by sliding friction.

7. A soil pollution monitoring device according to claim 2, characterized in that: The functional gear (21) and the sampling gear (23) are concentrically arranged, and the functional gear (21) and the ventilation rod (20) are concentrically designed.

8. A soil pollution monitoring device according to claim 2, characterized in that: The pressure chamber (24) and the piston plate (25) are connected by sliding friction, and the upper end of the piston plate (25) is flush with the upper end of the sampling plate (27).

9. A soil pollution monitoring device according to claim 2, characterized in that: The sampling plate (27) is designed to be arc-shaped, and the outer surface of the sampling plate (27) is in contact with the inner surface of the piston plate (25).

10. A soil pollution monitoring device according to claim 2, characterized in that: The sampling plate (27) and the central column (14) are eccentrically designed, and the minimum distance between the two ends of the sampling plate (27) is greater than the distance from the center of the ventilation rod (20) to the outer edge of the spiral plate (17).

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