Soil ecological environment monitoring device

Abstract

The invention relates to the technical field of soil detection, and discloses a soil ecological environment monitoring device which comprises a soil moisture content monitor, a plurality of positioning mechanisms are arranged on the soil moisture content monitor, and a caking crushing structure is arranged on each positioning mechanism; the multiple groups of position adjusting mechanisms comprise limiting cylinders, micro driving motors and inclined driving pieces, and the micro driving motors and the inclined driving pieces are arranged in the limiting cylinders and used for providing power and guiding; according to the soil monitoring device, the positioning mechanism and the caking crushing structure are creatively integrated, so that the accuracy and long-term effectiveness of soil monitoring are improved. The position adjusting mechanism adopts the synergistic effect of a micro driving motor and an inclined driving piece, the operation depth and angle of the caking crushing structure can be intelligently adjusted and controlled, and self-adaption to different soil environments is achieved.

Description

Technical Field

[0001] This invention relates to the field of soil testing, and more specifically, to a soil ecological environment monitoring device. Background Technology

[0002] Soil is one of the most complex ecosystems on Earth. It not only provides a medium for plant growth but also harbors countless microorganisms, animals, and organic matter. It is a key link in the material cycle and energy conversion of the ecosystem. With global climate change, accelerated industrialization, and continuous population growth, soil ecosystems face many challenges, such as soil degradation, pollution, and structural damage. Therefore, long-term and accurate monitoring of the soil ecological environment is particularly important. It can help us understand changes in soil status in a timely manner and provide a scientific basis for sustainable agricultural development, environmental protection, and ecological restoration.

[0003] Soil clumping is a common and challenging problem in practical soil monitoring. When soil is wetted by rainwater, the cohesion between soil particles increases. Subsequently, during the drying process, these particles form hard clumps that adhere directly to the surface of the detector probe column, acting like an "armor" for the probe column and severely hindering effective contact between the sensor and the soil. As a result, the data collected by the sensor cannot accurately reflect the true soil moisture, leading to significant data deviations and affecting the reliability of the monitoring results. To address this issue, we propose a soil ecological environment monitoring device. Summary of the Invention

[0004] This invention provides a soil ecological environment monitoring device, which solves the technical problem in related technologies that when soil clumps, the data collected by the sensor cannot accurately reflect the true soil moisture, resulting in large deviations in the monitoring data.

[0005] The present invention provides a soil ecological environment monitoring device, comprising: a soil moisture monitoring instrument, wherein the soil moisture monitoring instrument is provided with multiple sets of adjustment mechanisms, and each adjustment mechanism is provided with an agglomeration and crushing structure;

[0006] The multiple adjustment mechanism includes a limiting cylinder, a micro drive motor, and a tilting component. The micro drive motor and the tilting component are both located inside the limiting cylinder to provide power and guidance.

[0007] The agglomeration crushing structure includes a detection probe column, a sensor, and multiple sets of expansion components. The detection probe column is rotatably connected to the limiting cylinder. Each set of expansion components includes four expansion columns with drill bit patterns on the outer wall. Sensors are installed in the gaps between the four expansion columns. When the soil is soaked in water and then dries, a micro drive motor drives the multiple sets of expansion components to rotate. At the same time, the drive tilting component pushes the rotating expansion columns to expand outward, thereby crushing the soil agglomerates around the detection probe column. It can also drive the detection probe column to move in a fan shape, reducing the obstruction and interference of soil agglomerates on the sensor.

[0008] Furthermore, the soil moisture monitoring instrument is equipped with a connecting pipe at its connection end, and a ground column is installed at the end of the connecting pipe away from the soil moisture monitoring instrument, with a protective box installed on the ground column.

[0009] Furthermore, a limiting groove is provided at the bottom of the limiting cylinder, and the detection probe column passes through the inside of the limiting groove. The width of the limiting groove is greater than the diameter of the detection probe column.

[0010] Furthermore, the drive mechanism includes a universal joint connected to a micro drive motor. The universal joint includes a top section, a middle section, and a bottom section. The top section and the middle section form a telescopic structure, and the top post of the middle section passes through the top section. The middle section and the bottom section are rotatably connected.

[0011] Furthermore, the deflector also includes a positioning plate ring, which is fixedly connected to the limiting cylinder. An airbag ring is fixedly installed below the positioning plate ring, and several push plate air columns are fixedly installed on the lower wall of the airbag ring. The airbag ring and the several push plate air columns are interconnected.

[0012] Furthermore, the air inlet end of the airbag ring is connected to an air supply pipe, and the air supply pipe runs along the inside of the connecting pipe. The end of the connecting pipe away from the soil moisture monitor is connected to the intelligent air pump, and the intelligent air pump and the intelligent control module are set in the protective box.

[0013] Furthermore, a lifting plate ring is fixedly connected below the push plate air column, and a following plate ring is fixedly installed at the center of the lifting plate ring. The top column of the middle section of the universal shaft passes through the following plate ring, and the two are movably connected. At the same time, the diameter of the circular hole of the following plate ring is smaller than the diameter of the middle section of the universal shaft.

[0014] Furthermore, an inflatable air column is fixedly connected to both sides of the airbag ring. A solenoid valve is installed on the inflatable air column, and the end of the inflatable air column away from the airbag ring is fixedly connected to the top wall of the detection probe column. The two airbag rings are respectively pressed against the top wall of the detection probe column on both sides. The solenoid valve is connected to the intelligent control module in the protective box through wires.

[0015] Furthermore, the outer wall of the detection probe column is provided with several retractable grooves. Every four retractable grooves at the same height form a group. The expansion column is located in the retractable groove and is rotatably connected. A secondary gear disk is fixedly installed at the top of the expansion column. A universal ball is rotatably installed inside the secondary gear disk and is fixedly connected to the detection probe column.

[0016] Furthermore, a main gear disk is located at the center of the four auxiliary gear disks. The main gear disk and the auxiliary gear disk mesh with each other, and both the auxiliary gear disk and the main gear disk are frustoconical. The center of the main gear disk passes through a fixed connecting column, and the top of the connecting column is fixedly connected to the bottom section of the universal joint. There is a main gear disk between each set of auxiliary gear disks.

[0017] The beneficial effects of this invention are as follows:

[0018] This invention significantly improves the accuracy and long-term effectiveness of soil monitoring by innovatively integrating a positioning mechanism and a clod-crushing structure. The positioning mechanism, employing a micro-drive motor and a tilting component, intelligently adjusts the working depth and angle of the clod-crushing structure, achieving adaptability to different soil environments. When soil clods form due to wet-dry cycles, the expansion column, guided by centrifugal force and the tilting component, moves outward in a spiral motion. Its drill bit pattern effectively breaks up the clodded layer, preventing the sensor from being encased in a hard shell. This active crushing mechanism not only eliminates the signal attenuation problem caused by clod obstruction in traditional monitoring equipment but also promotes a balanced distribution of water and nutrients by periodically disturbing the soil structure, creating a better microenvironment for root growth.

[0019] By detecting the fan-shaped displacement of the probe column, the monitoring range is expanded in three dimensions and dynamically optimized. Driven by a micro-drive motor, the probe column can rotate around its axis in a fan shape, forming a fan-shaped monitoring area in conjunction with the radial expansion of the expansion column. This movement mode allows the sensor to overcome the limitations of fixed monitoring points and perform scanning detection of the soil environment within a 20cm radius, making it particularly suitable for precise monitoring of special micro-domains such as root zones and nutrient-rich zones. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the limiting cylinder structure of the present invention;

[0022] Figure 3 This is a schematic diagram of the micro drive motor structure of the present invention;

[0023] Figure 4 This is a schematic diagram of the positioning plate ring structure of the present invention;

[0024] Figure 5This is a schematic diagram of the lifting plate ring structure of the present invention;

[0025] Figure 6 This is a schematic diagram of the expansion column structure of the present invention;

[0026] Figure 7 This is the invention Figure 6 Enlarged view of point A in the middle;

[0027] Figure 8 This is a schematic diagram of the auxiliary gear disk structure of the present invention.

[0028] In the diagram: 11. Ground column; 12. Protective box; 13. Connecting pipe; 14. Soil moisture monitor; 2. Adjustment mechanism; 21. Limiting cylinder; 22. Limiting groove; 23. Miniature drive motor; 24. Air supply pipe; 25. Positioning plate ring; 26. Airbag ring; 27. Solenoid valve; 28. Expansion air column; 29. ​​Lifting plate ring; 201. Push plate air column; 202. Following plate ring; 3. Agglomeration and crushing structure; 31. Detection probe column; 32. Sensor; 33. Closing groove; 34. Expansion column; 35. Connecting column; 36. Main gear disk; 37. Secondary gear disk; 38. Universal ball; 41. Top section of universal shaft; 42. Middle section of universal shaft; 43. Bottom section of universal shaft. Detailed Implementation

[0029] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0030] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, a soil ecological environment monitoring device includes: a soil moisture monitor 14, which is equipped with multiple sets of adjustment mechanisms 2, and each adjustment mechanism 2 is equipped with a caking and crushing structure 3.

[0031] The multi-set adjustment mechanism 2 includes a limiting cylinder 21, a micro drive motor 23, and a drive component. The micro drive motor 23 and the drive component are both located inside the limiting cylinder 21 to provide power and guidance.

[0032] The agglomeration crushing structure 3 includes a detection probe column 31, a sensor 32, and multiple sets of expansion members. The detection probe column 31 is rotatably connected to the limiting cylinder 21. Each set of expansion members includes four expansion columns 34 with drill bit patterns on the outer wall. The sensor 32 is installed in the gap between the four expansion columns 34. When the soil is soaked in water and then dries, the micro drive motor 23 drives the multiple sets of expansion members to rotate. At the same time, the drive tilting member pushes the rotating expansion columns 34 to expand outward, thereby crushing the soil agglomerates around the detection probe column 31. It can also drive the detection probe column 31 to move in a fan shape, reducing the obstruction and interference of soil agglomerates on the sensor 32.

[0033] The soil moisture monitoring instrument 14 is equipped with a connecting pipe 13 at its connection end. A ground column 11 is installed at the end of the connecting pipe 13 away from the soil moisture monitoring instrument 14, and a protective box 12 is installed on the ground column 11.

[0034] A limiting groove 22 is provided at the bottom end of the limiting cylinder 21, and the detection probe column 31 passes through the inside of the limiting groove 22. The width of the limiting groove 22 is greater than the diameter of the detection probe column 31.

[0035] like Figure 5 and Figure 6 As shown, the drive mechanism includes a universal joint connected to the micro drive motor 23. The universal joint includes a top section 41, a middle section 42, and a bottom section 43. The top section 41 and the middle section 42 form a telescopic structure, and the top post of the middle section 42 passes through the top section 41. The middle section 42 and the bottom section 43 are rotatably connected.

[0036] The tilting component also includes a positioning plate ring 25, which is fixedly connected to the limiting cylinder 21. An airbag ring 26 is fixedly installed below the positioning plate ring 25. Several push plate air columns 201 are fixedly installed on the lower wall of the airbag ring 26, and the airbag ring 26 and the several push plate air columns 201 are interconnected.

[0037] The air inlet end of the airbag ring 26 is connected to the air supply pipe 24, and the air supply pipe 24 runs along the inside of the connecting pipe 13. The end of the connecting pipe 13 away from the soil moisture monitor 14 is connected to the intelligent air pump. The intelligent air pump and the intelligent control module are set in the protective box 12.

[0038] A lifting plate ring 29 is fixedly connected below the push plate air column 201. A following plate ring 202 is fixedly set at the center of the lifting plate ring 29. The top column of the universal shaft middle section 42 passes through the following plate ring 202 and the two are movably connected. At the same time, the diameter of the circular hole of the following plate ring 202 is smaller than the diameter of the universal shaft middle section 42.

[0039] like Figure 7 and Figure 8As shown, both sides of the airbag ring 26 are fixedly connected to an inflatable air column 28. An electromagnetic valve 27 is installed on the inflatable air column 28, and the end of the inflatable air column 28 away from the airbag ring 26 is fixedly connected to the top wall of the detection probe column 31. The two airbag rings 26 are respectively pressed against the top walls of the detection probe column 31. The electromagnetic valve 27 is connected to the intelligent control module in the protective box 12 through a wire.

[0040] The outer wall of the detection probe column 31 is provided with several retractable grooves 33. Every four retractable grooves 33 at the same height form a group. The expansion column 34 is located in the retractable grooves 33 and is rotatably connected. The top of the expansion column 34 is fixedly provided with a secondary gear disk 37. A universal ball 38 is rotatably provided inside the secondary gear disk 37 and is fixedly connected to the detection probe column 31.

[0041] A main gear disk 36 is located at the center of the four auxiliary gear disks 37. The main gear disk 36 and the auxiliary gear disks 37 mesh with each other. Both the auxiliary gear disks 37 and the main gear disks 36 are frustoconical. The center of the main gear disk 36 passes through the fixedly connected connecting post 35. The top of the connecting post 35 is fixedly connected to the bottom section 43 of the universal joint. There is a main gear disk 36 between each set of auxiliary gear disks 37.

[0042] The ground support column 11 is erected on the ground in the field. The ground support column 11 is also equipped with solar photovoltaic panels, while the protective box 12 is equipped with various auxiliary equipment, intelligent control modules and functional air pumps.

[0043] Afterwards, the soil moisture monitoring instrument 14 needs to be buried in the soil, or the detection probe column 31 needs to be inserted into the soil, and the entire device needs to be set up in the field for a long time.

[0044] After each rainfall, the rainwater soaks the soil, making the soil around the detection probe column 31 compact. After the soil dries, the soil adhering to the detection probe column 31 clumps together, affecting the sensor 32's detection of soil moisture. Under these conditions, the intelligent control module controls the air pump and the micro drive motor 23 to work. The micro drive motor 23 drives the connecting column 35 to rotate through the middle section 42 of the universal shaft. At this time, the main gear disk 36 drives the secondary gear disk 37 to rotate, causing the expansion column 34 to rotate in the converging groove 33, breaking up the surrounding soil.

[0045] The air pump flows into the airbag ring 26 through the air supply pipe 24. As the air pressure in the airbag ring 26 increases, multiple push plate air columns 201 extend and expand simultaneously. The extension of multiple push plate air columns 201 pushes the lifting plate ring 29 to move downward, and at the same time drives the follower plate ring 202 to move downward. The follower plate ring 202 pushes the middle section 42 and the bottom section 43 of the universal shaft to move downward by a preset length. At this time, the connecting column 35 and the main gear disk 36 are pushed downward. The main gear disk 36 presses down on the innermost side of the auxiliary gear disk 37. After being pressured, multiple expansion columns 34 rotate out of the collection groove 33 with the universal ball 38 as the center, forming a fan-shaped three-dimensional broken soil.

[0046] On the one hand, the fan-shaped three-dimensional soil fragmentation can reduce the influence of the soil clumping sensor 32; on the other hand, the multiple expansion columns 34 can fix the soil moisture monitor 14, reducing the possibility of tilting.

[0047] After all expansion columns 34 have rotated and expanded, the intelligent control module controls the solenoid valves 27 on the same side of multiple detection probe columns 31 to work, so that the air in the airbag ring 26 flows into the expansion column 28, causing the expansion column 28 to expand and extend, pushing the detection probe column 31 to rotate. The two solenoid valves 27 can be controlled to work alternately, so that the detection probe column 31 rotates in a fan shape.

[0048] On the one hand, it can break up clumps of soil over a large area, and on the other hand, it can fine-tune the position of the detection probe column 31.

[0049] Overall architecture and initial deployment:

[0050] A ground-mounted column 11 stands on the ground in the field, equipped with solar photovoltaic panels that convert solar energy into electricity, providing a continuous and stable energy supply for the entire device and meeting its power needs for long-term operation in the field. A protective box 12 is installed on the ground-mounted column 11, housing various auxiliary equipment, intelligent control modules, and key components such as a functional air pump. It serves a protective and integrated function, shielding internal components from the harsh outdoor environment while facilitating centralized management and control. A soil moisture monitor 14 is connected to the ground-mounted column 11 via a connecting pipe 13. The entire device needs to be permanently installed in the field, and during use, the soil moisture monitor 14 must be buried in the soil, or the detection probe column 31 must be inserted into the soil to ensure accurate monitoring of soil moisture.

[0051] Soil clumping monitoring and triggering mechanism:

[0052] In the field, after each rainfall, the soil becomes wet and compacted around the detection probe column 31. Subsequently, as the soil gradually dries, the soil adhering to the detection probe column 31 will clump together, directly affecting the accuracy of the sensor 32 in detecting soil moisture. The intelligent control module monitors the changes in soil condition in real time. Once soil clumping is detected, it automatically activates the corresponding response mechanism, controlling the air pump and micro drive motor 23 to enter working mode, providing power support for subsequent soil clumping and breaking operations.

[0053] Agglomeration and crushing process:

[0054] A miniature drive motor 23 serves as the power source, driving the connecting column 35 to rotate via a universal joint. The rotation of the connecting column 35 further drives the main gear disk 36 to rotate. Since the main gear disk 36 and the auxiliary gear disk 37 mesh with each other, and both the auxiliary gear disk 37 and the main gear disk 36 are frustoconical in shape, this special gear design ensures efficient power transmission and precise direction conversion during transmission. As the main gear disk 36 rotates, the auxiliary gear disk 37 rotates accordingly, thereby driving the expansion column 34 to rotate within the converging groove 33, breaking up the surrounding compacted soil. Simultaneously, an air pump begins supplying air to the airbag ring 26 via the air supply pipe 24. As the internal air pressure of the airbag ring 26 continuously increases, multiple pusher air columns 201 are simultaneously extended and expanded. The extension of the push plate air column 201 pushes the lifting plate ring 29 downward, causing it to move. The movement of the lifting plate ring 29 further drives the following plate ring 202 downward. Through the interaction between the following plate ring 202 and the middle section 42 of the universal joint, the middle section 42 and the bottom section 43 of the universal joint are pushed downward by a predetermined length. This series of actions ultimately causes the connecting column 35 and the main gear disk 36 to move downward. The main gear disk 36 exerts downward pressure on the secondary gear disk 37. After being subjected to pressure, the multiple expansion columns 34 smoothly rotate out of the converging groove 33 with the universal ball 38 as the center, forming a fan-shaped three-dimensional structure, thereby achieving effective breaking of the clumped soil.

[0055] Multi-stage crushing principle: Primary crushing: The expansion column has 34 drill bit patterns on the outer wall, a helix angle of 45°, and a tooth depth of 0.8mm, which generates shearing force.

[0056] Secondary crushing: The secondary gear disk has a 37-cone surface with a cone angle of 60°, forming a compression crushing process.

[0057] Level 3 crushing: The detection probe column 31 rotates at a speed of 3-5 rpm, generating eddy currents to loosen the material.

[0058] The adjustment process of probe column 31:

[0059] After all the expansion columns 34 have fully rotated and expanded, the intelligent control module precisely controls the opening of the solenoid valves 27 on the same side of the multiple detection probe columns 31, allowing air from the airbag ring 26 to flow into the expansion column 28. The expansion column 28 then expands and extends, pushing the detection probe columns 31 to rotate. By reasonably controlling the alternating operation of the two solenoid valves 27, the detection probe columns 31 can be made to rotate in a fan shape, further expanding the area of ​​soil fragmentation. At the same time, the position of the detection probe columns 31 can be finely adjusted to ensure that they are always in the optimal monitoring position.

[0060] The embodiments of the present invention have been described above, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms based on the guidance of the present embodiments, all of which are within the protection scope of the present embodiments.

Claims

1. A soil ecological environment monitoring device, characterized in that, include: Soil moisture monitoring instrument (14), the soil moisture monitoring instrument (14) is equipped with multiple sets of adjustment mechanisms (2), each adjustment mechanism (2) is equipped with a clogging and crushing structure (3); The multiple adjustment mechanism (2) includes a limiting cylinder (21), a micro drive motor (23) and a drive component. The micro drive motor (23) and the drive component are both located inside the limiting cylinder (21) to provide power and guidance. The agglomeration crushing structure (3) includes a detection probe column (31), a sensor (32), and multiple sets of expansion members. The detection probe column (31) is rotatably connected to the limiting cylinder (21). Each set of expansion members includes four expansion columns (34) with drill bit patterns on the outer wall. The sensor (32) is installed in the gap between the four expansion columns (34). When the soil dries after being soaked in water, the micro drive motor (23) drives the multiple sets of expansion members to rotate. At the same time, the drive tilting member pushes the rotating expansion column (34) to expand outward, thereby crushing the soil agglomeration around the detection probe column (31) and driving the detection probe column (31) to move in a fan shape, reducing the obstruction and interference of soil agglomeration on the sensor (32).

2. The soil ecological environment monitoring device according to claim 1, characterized in that, The soil moisture monitoring instrument (14) is equipped with a connecting pipe (13) at its connecting end. A ground column (11) is provided at the end of the connecting pipe (13) away from the soil moisture monitoring instrument (14). A protective box (12) is provided on the ground column (11).

3. The soil ecological environment monitoring device according to claim 1, characterized in that, The bottom end of the limiting cylinder (21) is provided with a limiting groove (22), and the detection probe column (31) passes through the inside of the limiting groove (22). The width of the limiting groove (22) is greater than the diameter of the detection probe column (31).

4. A soil ecological environment monitoring device according to claim 2, characterized in that, The drive mechanism includes a universal joint connected to a micro drive motor (23). The universal joint includes a top section (41), a middle section (42), and a bottom section (43). The top section (41) and the middle section (42) form a telescopic structure, and the top post of the middle section (42) passes through the top section (41). The middle section (42) and the bottom section (43) are rotatably connected.

5. A soil ecological environment monitoring device according to claim 4, characterized in that, The deflector also includes a positioning plate ring (25), which is fixedly connected to the limiting cylinder (21). An airbag ring (26) is fixedly arranged below the positioning plate ring (25). Several push plate air columns (201) are fixedly arranged on the lower wall of the airbag ring (26), and the airbag ring (26) and the several push plate air columns (201) are interconnected.

6. A soil ecological environment monitoring device according to claim 5, characterized in that, The air inlet end of the airbag ring (26) is connected to an air supply pipe (24), and the air supply pipe (24) runs along the inside of the connecting pipe (13). The end of the connecting pipe (13) away from the soil moisture monitor (14) is connected to the intelligent air pump. The intelligent air pump and the intelligent control module are set in the protective box (12).

7. A soil ecological environment monitoring device according to claim 6, characterized in that, A lifting plate ring (29) is fixedly connected below the push plate air column (201). A follower plate ring (202) is fixedly set at the center of the lifting plate ring (29). The top column of the middle section (42) of the universal shaft passes through the follower plate ring (202) and the two are movably connected. At the same time, the diameter of the circular hole of the follower plate ring (202) is smaller than the diameter of the middle section (42) of the universal shaft.

8. A soil ecological environment monitoring device according to claim 7, characterized in that, Both sides of the airbag ring (26) are fixedly connected to an expansion air column (28). An electromagnetic valve (27) is provided on the expansion air column (28). The end of the expansion air column (28) away from the airbag ring (26) is fixedly connected to the top wall of the detection probe column (31). The two airbag rings (26) are respectively pressed against the top walls of the detection probe column (31). The electromagnetic valve (27) is connected to the intelligent control module in the protective box (12) through a wire.

9. A soil ecological environment monitoring device according to claim 4, characterized in that, The outer wall of the detection probe column (31) is provided with several closing grooves (33). Every four closing grooves (33) at the same height form a group. The expansion column (34) is located in the closing groove (33) and is rotatably connected. A secondary gear disk (37) is fixedly provided at the top of the expansion column (34). A universal ball (38) is rotatably provided inside the secondary gear disk (37), and the universal ball (38) is fixedly connected to the detection probe column (31).

10. A soil ecological environment monitoring device according to claim 9, characterized in that, A main gear disk (36) is provided at the center of the four auxiliary gear disks (37). The main gear disk (36) and the auxiliary gear disk (37) mesh with each other. Both the auxiliary gear disk (37) and the main gear disk (36) are frustoconical. The center of the main gear disk (36) passes through the fixedly connected connecting column (35). The top of the connecting column (35) is fixedly connected to the bottom section (43) of the universal joint. A main gear disk (36) is provided between each set of auxiliary gear disks (37).

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