Bimetal thermometer with annular measuring surface

Abstract

The invention discloses a bimetal thermometer with an annular measuring surface, and belongs to the technical field of temperature detection devices, the bimetal thermometer with the annular measuring surface comprises a protection tube, a dial, a pointer shaft and a movable nut, and also comprises a mounting disc, a mounting cylinder, an end flange and a rear cover; the rotating part is rotationally connected to the rear cover, the rotating part is connected with the pointer shaft, and the rotating part and the pointer shaft synchronously rotate; the temperature sensing element is in a volute spiral spring shape, one end, corresponding to the axis of the mounting disc, of the temperature sensing element is fixedly connected to the periphery of the rotating part, the other end of the temperature sensing element is fixedly connected with a positioning pin, and the positioning pin penetrates through the end face of the rear cover. The temperature sensing element is arranged to be in a volute spiral spring shape, so that the temperature sensing element and the rotating part can form an annular measuring surface, the detection area of the temperature sensing element is greatly increased, compared with the prior art, the temperature of liquid levels with different heights within a certain range can be detected, and detection errors are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of temperature detection devices, and in particular relates to a bimetallic thermometer with an annular measuring surface. Background Art

[0002] The bimetallic thermometer combines two metals with different linear expansion coefficients and fixes one end. When the temperature changes, the two metals expand differently, causing the pointer to deflect to indicate the temperature. This is a bimetallic thermometer.

[0003] like Figure 1 As shown, the bimetallic thermometer generally includes a pointer 1a, a dial 1b, a case 1c, a movable nut 1d, a pointer shaft 1e, a protective tube 1f, a temperature sensing element 1g and a fixed end 1h, wherein the temperature sensing element 1g expands in volume during the heat transfer process, and the temperature sensing element 1g will rotate and drive the pointer shaft 1e to rotate, so that the pointer shaft 1e drives the pointer 1a to rotate, and the scale line value on the dial 1b indicated by the hovering position of the pointer 1a can be determined as the temperature value.

[0004] Another example is the patent publication number: CN 216746473 U, which discloses an adjustable bimetallic thermometer for measuring temperature, including a meter head and a temperature probe rod, the temperature probe rod is installed on the meter head, the temperature probe rod includes an inner temperature sensing part and an outer temperature sensing part, the outer temperature sensing part wraps the inner temperature sensing part, and the inner temperature sensing part can rotate relative to the outer temperature sensing part, a bimetallic spiral temperature sensing element is installed in the inner temperature sensing part, one end of the bimetallic spiral temperature sensing element is connected to the inner temperature sensing part, and the other end drives the pointer through the connecting part, the inner temperature sensing part is provided with a slotted or cross groove compatible with a common screwdriver, and the inner temperature sensing part is rotated with a screwdriver to drive the bimetallic spiral temperature sensing element to rotate synchronously, thereby driving the pointer to rotate, and it can perform temperature calibration, and has a simple structure, convenient installation, and low cost.

[0005] The temperature sensing element 1g in the above patent and the prior art has a columnar spiral structure, and therefore can only detect the heat within a limited linear range. For some measurement occasions, such as measuring the temperature below the liquid surface, the temperature will be different at different heights. At this time, the heat received by the spiral columnar thermal bimetal comes from different heights, resulting in a deviation in the measurement result. Therefore, the bimetallic thermometer in the prior art has a certain temperature detection error. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide a bimetallic thermometer with an annular measuring surface.

[0007] The technical solution adopted to solve the above technical problems is: A bimetallic thermometer with an annular measuring surface comprises a protective tube, a dial, a pointer shaft and a movable nut, and also comprises: A mounting plate, the end surface of which is fixedly connected to a mounting tube, the end of which is fixedly connected to an end flange, the end flange and the movable nut are respectively mounted on the inner and outer walls of the external container, and the end surface of the mounting plate facing away from the mounting tube is open and detachably connected to a rear cover; A rotating part rotatably connected to the back cover, the rotating part is connected to the pointer shaft, and the rotating part and the pointer shaft rotate synchronously; The temperature sensing element installed in the installation disk is in the shape of a spiral spring, and one end of the temperature sensing element corresponding to the axis of the installation disk is fixedly connected to the periphery of the rotating part, and the other end is fixedly connected with a positioning pin, and the positioning pin is penetrated through the end surface of the rear cover.

[0008] Furthermore, the rear cover is embedded with a ball bearing, and one end of the rotating part is fixedly inserted into the inner ring of the ball bearing.

[0009] Furthermore, the maximum diameter of the outer edge of the temperature sensing element is smaller than the inner diameter of the mounting plate.

[0010] Furthermore, a locking unit for limiting the rotation of the rotating part is provided on the outer wall of the rear cover.

[0011] Furthermore, the locking unit includes a connecting tube connected to the end face of the rear cover, a clamping sleeve is coaxially fixedly connected to one end of the connecting tube facing the rear cover, a locking shaft is coaxially fixedly connected to one end of the rotating part away from the pointer shaft, the clamping sleeve is provided with a clamping hole for the locking shaft to pass freely, a plurality of deformation slots penetrating the clamping holes are provided on the periphery of the clamping sleeve, and a shrinkage component for driving the elastic shrinkage of the clamping sleeve is provided in the connecting tube.

[0012] Furthermore, the contraction assembly includes a sliding sleeve engaged in the connecting tube, the sliding sleeve slides freely in the inner cavity of the connecting tube, the outer diameter of the clamping sleeve decreases successively in the direction away from the rear cover, the end face of the sliding sleeve is provided with a tapered hole for the clamping sleeve to engage, a baffle is fixedly connected to the inner cavity wall of the connecting tube, a push rod is coaxially fixed to the other end face of the sliding sleeve, the push rod penetrates the baffle and slides freely, the push rod is coaxially connected to a piston at one end away from the sliding sleeve, the piston slides freely in the connecting tube, and a storage cavity is surrounded by the end face of the piston and the surface of the baffle.

[0013] Furthermore, a replenishing port communicating with the storage cavity is provided on the periphery of the connecting tube.

[0014] Furthermore, the clamping sleeve is made of spring steel.

[0015] Furthermore, a connecting sleeve is fixedly connected to one end of the pointer shaft away from the degree dial, a connecting shaft is passed through the connecting sleeve, one end of the connecting shaft away from the connecting sleeve passes through the mounting disk and is key-connected to the rotating part, and a fine-tuning unit is provided in the connecting sleeve for driving the connecting shaft to rotate relative to the pointer shaft.

[0016] Furthermore, the fine-tuning unit includes a fine-tuning shaft passing through the periphery of the connecting sleeve, a through groove is opened on the periphery of the connecting shaft, an end gear is fixedly connected to the inner wall of one side of the through groove, the end gear is coaxial with the connecting shaft, a gear portion is provided at the portion where the fine-tuning shaft passes through the through groove, the gear portion is meshed with the outside of the end gear, and an adjustment port corresponding to the fine-tuning shaft is opened on the periphery of the mounting tube.

[0017] The beneficial effects of the present invention are as follows: In the present invention, by setting the temperature sensing element in the shape of a spiral spring, the temperature sensing element and the rotating part can form an annular measuring surface, which greatly increases the detection area of ​​the temperature sensing element. Compared with the prior art, the temperature of liquid levels at different heights within a certain range can be detected, thereby reducing the detection error. In the present invention, the storage chamber is filled with heat-conducting oil. When the temperature detection work is performed, the heat-conducting oil expands in volume due to the heat and pushes the piston to move in the direction away from the rear cover, so that the tapered hole on the sliding sleeve is separated from the clamping state with the clamping sleeve, so that the clamping sleeve is changed from an elastic contraction state to an elastic expansion state, and then the clamping state of the clamping hole on the clamping sleeve on the locking shaft disappears. At this time, the rotating part can rotate freely, avoiding the deviation of the pointer on the dial due to the shaking of the external container during transportation and debugging during non-detection operations, and during the detection operation, the heat transfer effect is used to enable the pointer to perform normal indication work; In the present invention, the fine-tuning shaft is manually rotated, and the gear portion on the fine-tuning shaft meshes and rotates with the end gear, thereby driving the connecting shaft to rotate relative to the pointer shaft, and then adjusting the pointer on the dial so that the pointer points to the correct zero position, thereby facilitating more accurate temperature detection operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the cross-sectional structure of a bimetallic thermometer in the prior art; Figure 2 It is a schematic diagram of the overall structure of a bimetallic thermometer with an annular measuring surface in the present invention; Figure 3 yes Figure 2 A schematic cross-sectional view of the middle structure; Figure 4 yes Figure 2 A schematic diagram of the structure from a side view angle; Figure 5It is a schematic diagram of the structure after the rear cover, temperature sensing element, rotating part and connecting shaft are assembled in the present invention; Figure 6 yes Figure 5 The schematic diagram of the structure from a side view after the rear cover is omitted; Figure 7 yes Figure 6 Schematic diagram of the explosion decomposition structure; Figure 8 yes Figure 5 A schematic diagram of the structure from a side view angle; Fig. 9 yes Figure 8 A schematic cross-sectional view of a part of the structure; Fig.10 It is a schematic diagram of the structure after the connecting shaft, pointer shaft and connecting sleeve are assembled in the present invention; Fig.11 yes Fig. 9 A schematic cross-sectional view of the middle structure; Fig.12 yes Fig.11 A magnified schematic diagram of the local structure at point A; Fig.13 It is a schematic cross-sectional structural diagram of the connecting tube in the present invention.

[0019] Reference numerals: 1. Dial; 2. Protective tube; 3. Movable nut; 4. End flange; 5. Adjustment port; 6. Mounting cylinder; 7. Mounting plate; 8. Back cover; 9. Cylinder cover; 10. Connecting cylinder; 11. Pointer shaft; 12. Connecting sleeve; 13. Connecting shaft; 14. Temperature sensing element; 15. Positioning pin; 16. Rotating part; 17. Supplementary port; 18. Locking shaft; 19. Sliding sleeve; 20. Piston; 21. Push rod; 22. Tapered hole; 23. Storage chamber; 24. Fine-tuning shaft; 25. End gear; 26. Gear part; 27. Baffle; 28. Clamping hole; 29. ​​Deformation joint; 30. Clamping sleeve. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] like Figure 2-Figure 12 As shown; The present embodiment provides a bimetallic thermometer with an annular measuring surface, comprising a protective tube 2, a dial 1, a pointer shaft 11 and a movable nut 3. A pointer is arranged in the dial 1. When the pointer shaft 11 moves along the axial direction of the protective tube 2, the pointer shaft 11 can drive the pointer to rotate accordingly, and cooperate with the scale line on the dial 1 indicated by the pointer, so as to perform temperature detection operation. In addition, the movable nut 3 is installed on the outer wall of the external container by means of bolts. The end of the protective tube 2 away from the dial 1 extends to the inside of the container. The inner wall of the container is also connected to an end flange 4 by bolts. The end face of the end flange 4 is coaxially fixed with a mounting tube 6. The end of the protective tube 2 away from the dial 1 is penetrated into the mounting tube 6, and the connection is sealed. The end of the mounting tube 6 away from the end flange 4 is coaxially fixed with a mounting plate 7. The end face of the mounting plate 7 facing away from the mounting tube 6 is open and detachably connected with a rear cover 8. A ball bearing is embedded in the end face of the rear cover 8, and a cylindrical rotating part 16 is inserted on the inner ring of the ball bearing, so that the rotating part 16 is rotatably connected to the rear cover 8, and the rotating part 16 is located in the mounting plate 7. A spline hole is opened on the end face of the rotating part 16, and a connecting shaft 13 is inserted in the spline hole in a key connection. The connecting shaft 13 is inserted into the mounting tube 6 and moves freely. The end of the pointer shaft 11 away from the dial 1 is fixedly connected with a connecting sleeve 12, and one end of the connecting shaft 13 is inserted into the connecting sleeve 12 and can rotate and slide freely. The end of the connecting shaft 13 away from the connecting sleeve 12 penetrates the mounting plate 7 and is key-connected with the rotating part 16. A rotatable fine-tuning shaft 24 is penetrated by the periphery of the connecting sleeve 12. A through groove is provided on the periphery of the connecting shaft 13. An end gear 25 is fixedly connected to the inner wall of one side of the through groove. The end gear 25 is coaxial with the connecting shaft 13. A gear part 26 is provided at the part where the fine-tuning shaft 24 penetrates into the through groove. The gear part 26 is meshed with the end gear 25. An adjustment port 5 corresponding to the fine-tuning shaft 24 is provided on the periphery of the mounting tube 6. A temperature sensing element 14 is installed in the mounting disk 7. The material of the temperature sensing element 14 can be conventionally selected by those skilled in the art. The outer contour of the temperature sensing element 14 is in the shape of a spiral spring, and one end of the temperature sensing element 14 corresponding to the axis of the mounting disk 7 is fixedly connected to the periphery of the rotating part 16, and the other end of the temperature sensing element 14 is fixedly connected to a positioning pin 15, and the positioning pin 15 is penetrated through the end surface of the rear cover 8, so that the temperature sensing element 14 can be fixed in the mounting disk 7. The maximum diameter of the outer edge of the temperature sensing element 14 is smaller than the inner diameter of the mounting disk 7, so that the temperature sensing element 14 has a certain contraction and expansion space in the mounting disk 7. When heat is transferred to the mounting disk 7, the temperature sensing element 14 expands in volume due to heat, and becomes expanded; the temperature sensing element and the rotating part can form an annular measuring surface, which greatly increases the detection area of ​​the temperature sensing element. Compared with the prior art, it can detect the temperature of liquid levels at different heights within a certain range, reducing the detection error.

[0022] Since the end with the largest outer diameter of the temperature sensing element 14 is fixed to the rear cover 8 by the positioning pin 15, the volume expansion of the temperature sensing element 14 will cause the rotating part 16 to rotate counterclockwise (refer to Figure 5 ), when the rotating part 16 rotates, it will synchronously drive the connecting shaft 13 to rotate, and when the connecting shaft 13 rotates, it will drive the fine-tuning shaft 24 to rotate. Since the fine-tuning shaft 24 and the connecting sleeve 12 are relatively fixed, when the fine-tuning shaft 24 rotates, it will drive the pointer shaft 11 to rotate. When the pointer shaft 11 rotates, it will drive the pointer on the dial 1 to swing, so as to display the temperature value; The end surface of the rear cover 8 is connected with a connecting tube 10, and the end of the connecting tube 10 facing away from the rear cover 8 is open and detachably connected with a tube cover 9. The end of the connecting tube 10 facing the rear cover 8 is coaxially fixed with a clamping sleeve 30, and the end of the rotating part 16 away from the pointer shaft 11 is coaxially fixed with a locking shaft 18. The clamping sleeve 30 is provided with a clamping hole 28 for the locking shaft 18 to pass freely, and the periphery of the clamping sleeve 30 is provided with a plurality of deformation seams 29 penetrating the clamping holes 28. A sliding sleeve 19 is clamped and installed in the connecting tube 10, and the sliding sleeve 19 slides freely in the inner cavity of the connecting tube 10. The outer diameter of the clamping sleeve 30 decreases in sequence in the direction away from the rear cover 8, and the end surface of the sliding sleeve 19 is provided with a tapered hole 22 for the clamping sleeve 30 to engage; A baffle 27 is fixedly connected to the inner wall of the connecting cylinder 10, and a push rod 21 is coaxially fixedly connected to the other end face of the sliding sleeve 19. The push rod 21 penetrates the baffle 27 and slides freely. The end of the push rod 21 away from the sliding sleeve 19 is coaxially connected to a piston 20. The piston 20 slides freely in the connecting cylinder 10, and a storage chamber 23 is formed between the end face of the piston 20 and the surface of the baffle 27. The storage chamber 23 is filled with heat transfer oil. The heat transfer oil has the characteristic of volume expansion when heated. When the volume of the heat transfer oil expands, it will drive the piston 20 to move in a direction away from the rear cover 8, and then the piston 20 drives the push rod 21 and the sliding sleeve 19 to move in a direction away from the rear cover 8. A replenishing port 17 that passes through the storage chamber 23 is provided on the periphery of the connecting cylinder 10. A sealing cover is installed on the replenishing port 17. When adding heat transfer oil to the storage chamber 23, the sealing cover is first opened, and then the heat transfer oil is injected into the storage chamber 23, and then the sealing cover is tightened to seal the inside of the storage chamber 23.

[0023] When performing temperature detection, the heat transfer oil expands due to heat and pushes the piston to move away from the rear cover, so that the tapered hole on the sliding sleeve is disengaged from the engaging state with the clamping sleeve, and the clamping sleeve is transformed from an elastically contracted state to an elastically expanded state, thereby causing the clamping state of the clamping hole on the clamping sleeve on the locking shaft to disappear. At this time, the rotating part can rotate freely, avoiding the deviation of the pointer on the dial due to the shaking of the external container during transportation and debugging during non-detection operations, and during detection operations, the heat transfer effect is utilized to enable the pointer to perform normal indication work.

[0024] The working principle of this embodiment is as follows: During the test, the heat of the fluid in the container is transferred to the connecting tube 10, and the heat-conducting oil in the connecting tube 10 expands due to the heat, driving the piston 20 to move away from the rear cover 8, thereby causing the piston 20 to drive the push rod 21 and the sliding sleeve 19 to move away from the rear cover 8, so that the tapered hole 22 on the sliding sleeve 19 is separated from the engagement state with the clamping sleeve 30, so that the clamping sleeve 30 is changed from an elastic contraction state to an elastic expansion state, thereby causing the clamping state of the clamping hole 28 on the clamping sleeve 30 on the locking shaft 18 to disappear. At this time, the rotating part 16 can rotate freely. After the test is completed, the fluid in the container is taken out, and the temperature in the container drops. At this time, the volume of the heat transfer oil begins to shrink slowly, and the sliding sleeve 19 moves toward the direction of the rear cover 8, so that the tapered hole 22 is engaged with the periphery of the clamping sleeve 30, and an extrusion force is generated on the clamping sleeve 30 along the radial inner side of the clamping sleeve 30, so that the clamping sleeve 30 produces elastic contraction deformation, and the clamping hole 28 clamps the locking shaft 18. In addition, the clamping sleeve 30 is made of spring steel, so that the elastic deformation ability of the clamping sleeve 30 is better. The temperature sensing element 14 expands in volume due to heat, and the temperature sensing element 14 will be in an expanded state. Since the end with the largest diameter of the outer edge of the temperature sensing element 14 is fixed to the rear cover 8 by the positioning pin 15, the expansion of the temperature sensing element 14 will cause the rotating part 16 to rotate counterclockwise (refer to Figure 5 ), when the rotating part 16 rotates, it will synchronously drive the connecting shaft 13 to rotate, and when the connecting shaft 13 rotates, it will drive the fine-tuning shaft 24 to rotate. Since the fine-tuning shaft 24 and the connecting sleeve 12 are relatively fixed, when the fine-tuning shaft 24 rotates, it will drive the pointer shaft 11 to rotate. When the pointer shaft 11 rotates, it will drive the pointer on the dial 1 to swing, so as to display the temperature value; If the pointer on the dial 1 does not indicate the correct zero position when the temperature sensing element 14 is in the initial state, an external tool is used to pass through the adjustment port 5 and inserted into the hexagonal hole opened at the top of the fine-tuning shaft 24 to rotate the fine-tuning shaft 24. The gear portion 26 on the fine-tuning shaft 24 meshes and rotates with the end gear 25, thereby driving the connecting shaft 13 to rotate relative to the pointer shaft 11, and driving the pointer on the dial 1 to rotate, so that the pointer points to the correct zero position, which is convenient for more accurate temperature detection operations.

[0025] Although this specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0026] Therefore, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application; that is, all equivalent changes made according to the scope of the claims of the present application are within the protection scope of the claims of the present application.

Claims

1. A bimetallic thermometer having an annular measuring surface, comprising a protective tube (2), a dial (1), a pointer shaft (11) and a movable nut (3), characterized in that: Also includes: a mounting plate (7), the end surface of the mounting plate (7) being fixedly connected to a mounting tube (6), the end of the mounting tube (6) being fixedly connected to an end flange (4), the end flange (4) and the movable nut (3) being respectively mounted on the inner and outer walls of the external container in cooperation with each other, the end surface of the mounting plate (7) facing away from the mounting tube (6) being open and detachably connected to a rear cover (8); A rotating part (16) rotatably connected to the rear cover (8), the rotating part (16) being connected to the pointer shaft (11), and the rotating part (16) and the pointer shaft (11) rotating synchronously; A temperature sensing element (14) is installed in the mounting plate (7), the temperature sensing element (14) is in the shape of a spiral spring, and one end of the temperature sensing element (14) corresponding to the axis of the mounting plate (7) is fixedly connected to the periphery of the rotating portion (16), and the other end of the temperature sensing element (14) is fixedly connected to a positioning pin (15), and the positioning pin (15) is penetrated through the end surface of the rear cover (8).

2. The bimetallic thermometer with an annular measuring surface according to claim 1, characterized in that: The rear cover (8) is embedded with a ball bearing, and one end of the rotating part (16) is fixedly inserted into the inner ring of the ball bearing.

3. The bimetallic thermometer with an annular measuring surface according to claim 1, characterized in that: The maximum diameter of the outer edge of the temperature sensing element (14) is smaller than the inner diameter of the mounting plate (7).

4. The bimetallic thermometer with an annular measuring surface according to claim 1, characterized in that: A locking unit for limiting the rotation of the rotating part (16) is provided on the outer wall of the rear cover (8).

5. The bimetallic thermometer with an annular measuring surface according to claim 4, characterized in that: The locking unit comprises a connecting tube (10) connected to the end surface of the rear cover (8); a clamping sleeve (30) is coaxially fixedly connected to one end of the connecting tube (10) facing the rear cover (8); a locking shaft (18) is coaxially fixedly connected to one end of the rotating portion (16) away from the pointer shaft (11); a clamping hole (28) is formed in the clamping sleeve (30) for the locking shaft (18) to pass freely; a plurality of deformation slots (29) penetrating the clamping holes (28) are formed on the periphery of the clamping sleeve (30); and a contraction component for driving the clamping sleeve (30) to elastically contract is provided in the connecting tube (10).

6. The bimetallic thermometer with an annular measuring surface according to claim 5, characterized in that: The shrinking assembly comprises a sliding sleeve (19) engaged in the connecting tube (10), the sliding sleeve (19) sliding freely in the inner cavity of the connecting tube (10), the outer diameter of the clamping sleeve (30) decreasing in sequence in the direction away from the rear cover (8), the end surface of the sliding sleeve (19) is provided with a tapered hole (22) for the clamping sleeve (30) to engage, the inner cavity wall of the connecting tube (10) is fixedly connected with a baffle (27), the other end surface of the sliding sleeve (19) is coaxially fixedly connected with a push rod (21), the push rod (21) penetrates the baffle (27) and slides freely, the end of the push rod (21) away from the sliding sleeve (19) is coaxially connected with a piston (20), the piston (20) slides freely in the connecting tube (10), and a storage cavity (23) is surrounded by the end surface of the piston (20) and the surface of the baffle (27).

7. The bimetallic thermometer with an annular measuring surface according to claim 6, characterized in that: The connection tube (10) is provided with a replenishing port (17) on the periphery thereof and communicating with the storage cavity (23).

8. The bimetallic thermometer with an annular measuring surface according to claim 7, characterized in that: The clamping sleeve (30) is made of spring steel.

9. The bimetallic thermometer with an annular measuring surface according to claim 1, characterized in that: A connecting sleeve (12) is fixedly connected to one end of the pointer shaft (11) away from the degree disk (1), a connecting shaft (13) is inserted into the connecting sleeve (12), one end of the connecting shaft (13) away from the connecting sleeve (12) is inserted into the mounting plate (7) and is key-connected to the rotating part (16), and a fine-tuning unit for driving the connecting shaft (13) to rotate relative to the pointer shaft (11) is provided in the connecting sleeve (12).

10. The bimetallic thermometer with an annular measuring surface according to claim 9, characterized in that: The fine-tuning unit comprises a fine-tuning shaft (24) passing through the periphery of the connecting sleeve (12); a through slot is provided on the periphery of the connecting shaft (13); an end gear (25) is fixedly connected to an inner wall of one side of the through slot; the end gear (25) is coaxial with the connecting shaft (13); a gear portion (26) is provided at the portion where the fine-tuning shaft (24) passes through the through slot; the gear portion (26) is meshed with the outside of the end gear (25); and an adjustment port (5) corresponding to the fine-tuning shaft (24) is provided on the periphery of the mounting tube (6).

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