Gear box with lubrication control mechanism

Abstract

The invention relates to the technical field of gear boxes, and discloses a gear box with a lubrication control mechanism, which comprises an end cover, an upper cover is fixed at the upper end of the end cover, a rotatable gear set is arranged between the end cover and the upper cover, and a lubrication mechanism is arranged in the end cover. The lubricating mechanism comprises a first rotating shaft, a second rotating shaft, a third rotating shaft and a transmission belt. The first rotating shaft is matched with the gear set, the transmission belt is arranged on the first rotating shaft, the second rotating shaft and the third rotating shaft in a transmission mode, the second rotating shaft is used for adjusting the tightness degree of the transmission belt, and the third rotating shaft is used for driving lubricating oil to splash. Due to the fact that the third rotating shaft is hollow and can float on lubricating oil, the third rotating shaft can be kept on the liquid level of the lubricating oil by adjusting the first supporting shaft and the second supporting shaft, when the fan blades rotate on the liquid level of the lubricating oil, the fan blades can make direct contact with the lubricating oil on the liquid level, the lubricating oil is thrown out through centrifugal force, and the splashing effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of gear boxes, in particular to a gear box with a lubrication control mechanism. Background Art

[0002] The core function of the gearbox is to change the speed and torque of the output shaft through the combination of gears with different numbers of teeth. When the power of the input shaft remains unchanged, the speed of the output shaft is inversely proportional to the torque. By selecting the appropriate gear ratio, the output shaft can obtain the required speed and torque to meet various working requirements.

[0003] Lubricating oil plays a vital role in the gearbox. It can not only reduce the friction and wear between the gears and bearings, improve the working efficiency of the gearbox, but also effectively remove the heat generated during operation to prevent the gears and bearings from overheating and damage. In addition, lubricating oil also has good anti-rust and anti-corrosion functions, which can protect the metal parts inside the gearbox from corrosion and damage. During the operation of the gearbox, the lubricating oil circulates continuously to remove impurities and wear products on the gears and bearings, keeping the inside of the gearbox clean. At the same time, suitable lubricating oil can also form a stable oil film, so that the gears and bearings can maintain non-contact rolling and sliding during operation, further reducing friction and wear.

[0004] During the use of the gearbox, part of the lubricating oil may be lost due to volatilization, especially in a high temperature or poorly ventilated environment, the volatilization rate may be faster. The lubricating oil will oxidize and decompose under the action of high temperature and oxygen to produce some low molecular weight substances, which may evaporate and cause a reduction in oil volume.

[0005] Based on this, the lubricating oil will gradually decrease. In order to keep the gears in the gearbox in contact with the lubricating oil during rotation and to avoid as much as possible the impurities that settle to the bottom of the lubricating oil from contacting the gears again, improvements are proposed to the existing gearbox. Summary of the invention

[0006] The object of the present invention is to provide a gear box with a lubrication control mechanism to solve the problems raised in the above background technology.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a gear box with a lubrication control mechanism, comprising an end cover, an upper cover is fixed to the upper end of the end cover, a rotatable gear set is installed between the end cover and the upper cover, a lubrication mechanism is installed inside the end cover, and the lubrication mechanism includes a first rotating shaft, a second rotating shaft, a third rotating shaft and a transmission belt;

[0008] The rotating shaft 1 cooperates with the gear set, the transmission belt is arranged on the rotating shaft 1, the rotating shaft 2 and the rotating shaft 3, the rotating shaft 2 is used to adjust the tightness of the transmission belt, and the rotating shaft 3 is used to drive the lubricating oil to splash;

[0009] The rotating shaft 3 is flush with the lubricating oil and floats on the liquid surface of the lubricating oil;

[0010] The inner walls on both sides of the end cover are provided with longitudinally arranged sliding grooves and transversely extending mounting holes, and the sliding grooves and mounting holes are used to limit the first rotating shaft, the second rotating shaft and the third rotating shaft.

[0011] Furthermore, two sets of limit strips are fixed on the inner walls on both sides of the end cover, and the two sets of limit strips are respectively located on the corners of the slide slot and cooperate with the slide slot;

[0012] A support block 1 and a support block 2 are slidably provided in the slide grooves on both sides, and the support block 1 and the support block 2 are limited in the slide groove by the outer limiting strips, the support block 1 is located at the upper end of the support block 2, and the two ends of the rotating shaft 2 are respectively rotatably connected to the support block 1 on both sides, and the two ends of the rotating shaft 3 are respectively rotatably connected to the support block 2 on both sides;

[0013] The two ends of the rotating shaft 1 extend into the mounting holes on both sides respectively, and the rotating shaft 1 can rotate.

[0014] Furthermore, a lower opening is provided at the lower end of the limiting strip to facilitate the debris in the chute to move out from the lower opening.

[0015] Furthermore, transmission wheels are fixed on the rotating shaft one, the rotating shaft two and the rotating shaft three, and the transmission belt is sleeved into the transmission wheel and pressed against the inner wall of the transmission wheel.

[0016] Furthermore, the rotating shaft 1 is divided into two sleeve shaft sections and one inner shaft section, the two sleeve shaft sections are sleeved at both ends of the inner shaft, and the two sleeve shaft sections are fixed to the inner shaft by bolts;

[0017] A driving gear is fixed on both sleeve shaft sections, and the driving gear is used to mesh with the gear set.

[0018] Furthermore, the rotating shaft three is made of plastic material and is hollow inside. The outer side of the rotating shaft three has fan blades for driving the lubricating oil to splash. The supporting blocks two at both ends are also made of plastic material and are hollow inside.

[0019] Furthermore, a second support shaft is provided at the upper end of the second support block, and the second support shaft passes through the first support block upward and extends upward out of the upper cover;

[0020] A support shaft 1 is installed at the upper end of the support block 1, and the support shaft 1 also extends upward from the upper cover. The positions where the support shaft 1 and the support shaft 2 extend upward are sealed.

[0021] Furthermore, the second support shaft is in contact with the second support block, the upper end of the upper cover is fixed with a second frame rod, the upper end of the second frame rod is fixed with a transverse threaded barrel, the inner thread of the threaded barrel is connected with a fastening screw, the second support shaft passes through the second frame rod upward, and the fastening screw abuts against the second support shaft;

[0022] The support shaft 1 is fixed to the support block 1, a frame rod 1 is fixed to the upper end of the upper cover, a fastening nut is rotatably installed on the upper end of the frame rod 1, and the support shaft 1 upwardly penetrates the frame rod 1 and the fastening nut and is threadedly connected to the fastening nut.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0024] 1. The gear set works, and the driving gear rotates. Under the action of the transmission belt, the three outer blades of the shaft drive the lubricating oil, so that the lubricating oil splashes onto the gear set to complete the lubrication.

[0025] 2. Since the interior of the rotating shaft 3 is hollow, it can float on the lubricating oil. By adjusting the supporting shaft 1 and the supporting shaft 2, the rotating shaft 3 can be kept on the surface of the lubricating oil. When the fan blades rotate on the surface of the lubricating oil, they will directly contact the lubricating oil on the surface and throw the lubricating oil out through centrifugal force, forming a splashing effect. This splashing effect is usually more violent because the direct force and centrifugal force of the fan blades on the lubricating oil are very large. Compared with the contact between the gear set and the lubricating oil, the splashing effect will be improved to a certain extent, and can affect more gears to keep the gears lubricated.

[0026] 3. Keep the rotating shaft three-way above the lubricating oil surface to avoid contact with the bottom layer of lubricating oil. It can relatively keep the debris at the lower end deposited to the lower end of the lubricating oil to avoid it from rising upwards, thus avoiding scratches and wear on gears, bearings and other components. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 It is a schematic diagram of the lubrication mechanism and gear set structure of the present invention;

[0030] Figure 3 It is a schematic diagram of the structure of the lubrication mechanism of the present invention;

[0031] Figure 4 It is a schematic diagram of the main structure of the lubrication mechanism of the present invention;

[0032] Figure 5 It is a schematic diagram of the structure of the interior of the chute of the present invention;

[0033] Figure 6 It is a schematic diagram of the upper end structure of the support shaft 1 and the support shaft 2 of the present invention;

[0034] Figure 7 It is a schematic diagram of the structure of the first rotating shaft, the second rotating shaft and the third rotating shaft of the present invention;

[0035] Figure 8 It is a schematic diagram of the structure of the lubrication mechanism of the present invention installed in the end cover.

[0036] In the figure: 1. end cover; 11. upper cover; 12. slide groove; 13. mounting hole; 2. gear set; 3. lubrication mechanism; 31. limit strip; 311. lower opening; 32. rotating shaft 1; 321. driving gear; 322. sleeve shaft; 323. inner shaft; 33. rotating shaft 2; 331. supporting block 1; 332. supporting shaft 1; 333. rack rod 1; 334. fastening nut; 34. rotating shaft 3; 341. supporting block 2; 342. supporting shaft 2; 343. rack rod 2; 344. threaded barrel; 345. fastening screw; 35. transmission wheel; 36. transmission belt. DETAILED DESCRIPTION

[0037] 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.

[0038] See also Figure 1-Figure 8 The present invention provides a technical solution: there is a gap between the lower end of the gear set 2 and the inner wall of the lower end of the end cover 1. During use, the lubricating oil will gradually decrease under the influence of external conditions, and there may be a situation where the gear set 2 and the lubricating oil at the lower end are not in contact. In another case, the gap between the lower end of the gear set 2 and the inner wall of the lower end of the end cover 1 is small. Keeping the lubricating oil in contact with the gear set 2 will also bring up the debris settled at the lower end during the rotation of the gear set 2, affecting the life of the gear set 2. A gear box with a lubrication control mechanism is proposed, such as Figure 1 and Figure 2 As shown, it includes an end cover 1, an upper cover 11 is fixed to the upper end of the end cover 1, a rotatable gear set 2 is installed between the end cover 1 and the upper cover 11, and a lubrication mechanism 3 is installed inside the end cover 1. Figure 3As shown, the lubrication mechanism 3 includes a rotating shaft 1 32, a rotating shaft 2 33, a rotating shaft 34 and a transmission belt 36. Under the action of the gear set 2, the lubrication mechanism 3 is driven to work;

[0039] The rotating shaft 1 32 cooperates with the gear set 2, and the transmission belt 36 is arranged on the rotating shaft 1 32, the rotating shaft 2 33 and the rotating shaft 3 34. The rotating shaft 2 33 is used to adjust the tightness of the transmission belt 36, and the rotating shaft 3 34 is used to drive the lubricating oil to splash, so as to transmit the power generated by the gear set 2, so that the lubricating mechanism 3 can work accordingly;

[0040] The rotating shaft 34 is flush with the lubricating oil and floats on the surface of the lubricating oil, which can better splash the lubricating oil and also avoid lifting the deposited debris upwards, which will affect the life of the gear set 2 and the bearings;

[0041] like Figure 2 As shown, longitudinally arranged slide grooves 12 and transversely extending mounting holes 13 are provided on the inner walls on both sides of the end cover 1, and the slide grooves 12 and the mounting holes 13 are used to limit the rotating shaft 1 32, the rotating shaft 2 33 and the rotating shaft 3 34, and the slide grooves 12 and the mounting holes 13 are used to limit the lubrication mechanism 3.

[0042] like Figure 3 As shown, two sets of limit strips 31 are fixed on the inner walls of both sides of the end cover 1. The two sets of limit strips 31 are respectively located on the corners of the slide groove 12 and cooperate with the slide groove 12. In order to limit the lubrication mechanism 3, two sets of limit strips 31 are set to clamp the lubrication mechanism 3, and the lubrication mechanism 3 can also be moved up and down along the slide groove 12 and the limit strips 31.

[0043] like Figure 3 As shown, support blocks 1 331 and 341 are slidably provided in the slide grooves 12 on both sides, and the support blocks 1 331 and 341 are limited in the slide grooves 12 by the outer limiting strips 31, and the support blocks 1 331 are located at the upper end of the support blocks 2 341, and the two ends of the rotating shaft 2 33 are respectively rotatably connected with the support blocks 1 331 on both sides, and the two ends of the rotating shaft 34 are respectively rotatably connected with the support blocks 2 341 on both sides, and the support blocks 1 331 and 341 are used to limit the rotating shaft 2 33 and the rotating shaft 3 34, and enable the rotating shaft 2 33 and the rotating shaft 3 34 to move in the up and down directions;

[0044] Both ends of the rotating shaft 32 extend into the mounting holes 13 on both sides respectively, and the rotating shaft 32 can rotate, so that the rotating shaft 32 is limited and can rotate.

[0045] like Figure 5As shown, a lower opening 311 is provided at the lower end of the limit strip 31, so that debris in the chute 12 can move out from the lower opening 311. Debris deposited downward will move into the chute 12, and debris stuck in the corners of the chute 12 and the limit strip 31 will be difficult to separate. The lower opening 311 is provided at the lower end, which can reduce the formation of corners and facilitate the direct separation of debris in the chute 12.

[0046] like Figure 7 As shown, in order to limit the transmission belt 36, a transmission wheel 35 is fixed on the rotating shaft 1 32, the rotating shaft 2 33 and the rotating shaft 34, and the transmission belt 36 is sleeved into the transmission wheel 35 and squeezed with the inner wall of the transmission wheel 35, as shown in FIG. Figure 4 As shown, the transmission belt 36 forms a triangular shape. The second rotating shaft 33 moves downward to loosen the transmission belt 36, and moves upward to tighten the transmission belt 36.

[0047] like Figure 7 As shown, the rotating shaft 1 32 is divided into two sleeve shafts 322 and one inner shaft 323. The two sleeve shafts 322 are sleeved at both ends of the inner shaft 323, and the two sleeve shafts 322 and the inner shaft 323 are fixed by bolts. The two sleeve shafts 322 and one inner shaft 323 are convenient for matching with the mounting hole 13 and are also convenient for disassembly. By disassembling the rotating shaft 1 32 and then lifting the upper cover 11, the entire lubrication mechanism 3 can be separated.

[0048] like Figure 7 As shown, driving gears 321 are fixed on both sleeve shafts 322 , and the driving gears 321 are used to mesh with the gear set 2 , so that the lubrication mechanism 3 works when the gear set 2 works.

[0049] like Figure 7 As shown, the rotating shaft 34 is made of plastic and is hollow inside. The outer side of the rotating shaft 34 has fan blades for driving the lubricating oil to splash. The supporting blocks 2 341 at both ends are also made of plastic and are hollow inside, so that the rotating shaft 34 can float smoothly on the surface of the lubricating oil.

[0050] like Figure 5 and Figure 6 As shown, a second support shaft 342 is disposed at the upper end of the second support block 341, and the second support shaft 342 penetrates the first support block 331 upward and extends upward out of the upper cover 11;

[0051] A support shaft 1 332 is installed at the upper end of the support block 1 331, and the support shaft 1 332 also extends upward from the upper cover 11. The position where the support shaft 1 332 and the support shaft 2 342 extend upward is a sealing setting. The positions of the support blocks 1 331 and 341 are controlled by the support shaft 1 332 and the support shaft 2 342, so that the support block 2 341 floats to the surface of the lubricating oil and the transmission belt 36 is tightened.

[0052] The second support shaft 342 contacts the second support block 341, and a second frame rod 343 is fixed to the upper end of the upper cover 11. A horizontal threaded cylinder 344 is fixed to the upper end of the second frame rod 343. A fastening screw 345 is connected to the inner thread of the threaded cylinder 344. The second support shaft 342 passes through the second frame rod 343 upward, and the fastening screw 345 abuts against the second support shaft 342.

[0053] The support shaft 1 332 is fixed to the support block 1 331, and a frame rod 1 333 is fixed to the upper end of the upper cover 11. A fastening nut 334 is rotatably installed on the upper end of the frame rod 1 333. The support shaft 1 332 passes through the frame rod 1 333 and the fastening nut 334 upward and is threadedly connected with the fastening nut 334. The fastening nut 334 is controlled by the fastening screw 345 to control the movement of the support shaft 2 342 and the support shaft 1 332;

[0054] like Figure 8 The diagram shows the state where the lubrication mechanism 3 is installed inside the end cover 1, so that the second rotating shaft 33 and the third rotating shaft 34 can be adjusted, and the third rotating shaft 34 floats on the liquid surface.

[0055] The working principle of the present invention is as follows: there is a gap between the lower end of the gear set 2 and the inner wall of the lower end of the end cover 1. During use, the lubricating oil will gradually decrease under the influence of external conditions, and there may be a situation where the gear set 2 and the lubricating oil at the lower end are not in contact. In another case, the gap between the lower end of the gear set 2 and the inner wall of the lower end of the end cover 1 is small, and the lubricating oil is kept in contact with the gear set 2. During the rotation of the gear set 2, the debris settled at the lower end will also be brought upward, affecting the life of the gear set 2. Based on this, a lubrication mechanism 3 is proposed, and its specific operation is as follows:

[0056] During the operation of the gear set 2, the driving gear 321 rotates, and under the action of the transmission belt 36, the shaft 34 rotates, so that the outer blades of the shaft 34 drive the lubricating oil, so that the lubricating oil splashes onto the gear set 2 to complete the lubrication.

[0057] Secondly, since the interior of the rotating shaft 34 is hollow and can float on the lubricating oil, the fastening screw 345 is loosened to lift the support shaft 2 342 upward so that the upper end of the support block 2 341 has no support, and the fastening nut 334 is rotated at the same time to make the support shaft 1 332 move downward to loosen the transmission belt 36. Under the action of little or no external force, the rotating shaft 34 can float to the liquid surface of the lubricating oil, and then the support shaft 2 342 is pushed downward. When it is pushed to the upper end of the support block 2 341, there is a certain tactile feeling, that is, the rotating shaft 34 floats to the liquid surface of the lubricating oil, and then the support shaft 2 342 contacts the support block 2 341, and the fastening screw 345 is rotated to fix the support shaft 2 342, so that the rotating shaft 3 34 cannot move upward, then the fastening nut 334 is rotated to make the support shaft 1 332 move upward, and the rotating shaft 2 33 also moves upward, and the transmission belt 36 is supported again to ensure that the transmission belt 36 rotates to drive the rotating shaft 34 to rotate. After adjusting the support shaft 1 332 and the support shaft 2 342, the rotating shaft 34 can be kept on the lubricating oil surface. When the fan blade rotates on the lubricating oil surface, it will directly contact the lubricating oil on the liquid surface and throw the lubricating oil out through centrifugal force to form a splashing effect. This splashing effect is usually more intense because the direct force and centrifugal force of the fan blade on the lubricating oil are very large. Compared with the contact between the gear set 2 and the lubricating oil, the splashing effect will be improved to a certain extent, and can affect more gears to keep the gears lubricated.

[0058] In addition, keeping the rotating shaft 34 above the lubricating oil surface can avoid contact with the bottom layer of lubricating oil, and can relatively keep the debris at the lower end deposited to the lower end of the lubricating oil to avoid being lifted upward, thereby avoiding scratches and wear on gears, bearings and other components.

[0059] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0060] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A gearbox with a lubrication control mechanism, comprising an end cover (1), an upper cover (11) being fixed to the upper end of the end cover (1), a rotatable gear set (2) being mounted between the end cover (1) and the upper cover (11), characterized in that: A lubrication mechanism (3) is installed inside the end cover (1), and the lubrication mechanism (3) comprises a first rotating shaft (32), a second rotating shaft (33), a third rotating shaft (34) and a transmission belt (36); The rotating shaft (32) cooperates with the gear set (2), the transmission belt (36) is arranged on the rotating shaft (32), the rotating shaft (33) and the rotating shaft (34), the rotating shaft (33) is used to adjust the tightness of the transmission belt (36), and the rotating shaft (34) is used to drive the lubricating oil to splash; The rotating shaft 3 (34) is flush with the lubricating oil and floats on the liquid surface of the lubricating oil; The inner walls on both sides of the end cover (1) are provided with longitudinally arranged sliding grooves (12) and transversely extending mounting holes (13), and the sliding grooves (12) and mounting holes (13) are used to limit the positions of the first rotating shaft (32), the second rotating shaft (33) and the third rotating shaft (34).

2. The gearbox with lubrication control mechanism according to claim 1, characterized in that: Two sets of limit strips (31) are fixed on the inner walls on both sides of the end cover (1), and the two sets of limit strips (31) are respectively located on the corners of the slide groove (12) and cooperate with the slide groove (12); A support block 1 (331) and a support block 2 (341) are slidably provided in the slide grooves (12) on both sides. The support block 1 (331) and the support block 2 (341) are limited in the slide grooves (12) by the outer limiting strips (31). The support block 1 (331) is located at the upper end of the support block 2 (341). The two ends of the rotating shaft 2 (33) are respectively rotatably connected to the support blocks 1 (331) on both sides. The two ends of the rotating shaft 3 (34) are respectively rotatably connected to the support blocks 2 (341) on both sides. The two ends of the rotating shaft 1 (32) extend into the mounting holes (13) on both sides respectively, and the rotating shaft 1 (32) can rotate.

3. The gearbox with lubrication control mechanism according to claim 2, characterized in that: A lower opening (311) is provided at the lower end of the limiting strip (31) to facilitate the movement of debris in the slide groove (12) out of the lower opening (311).

4. The gearbox with lubrication control mechanism according to claim 2, characterized in that: The first rotating shaft (32), the second rotating shaft (33) and the third rotating shaft (34) are all fixed with transmission wheels (35), and the transmission belt (36) is sleeved inside the transmission wheel (35) and pressed against the inner wall of the transmission wheel (35).

5. The gearbox with lubrication control mechanism according to claim 2, characterized in that: The rotating shaft (32) is divided into two sleeve shafts (322) and an inner shaft (323). The two sleeve shafts (322) are sleeved at two ends of the inner shaft (323), and the two sleeve shafts (322) are fixed to the inner shaft (323) by bolts. A driving gear (321) is fixed on both sections of the sleeve shaft (322), and the driving gear (321) is used to mesh with the gear set (2).

6. The gearbox with lubrication control mechanism according to claim 2, characterized in that: The rotating shaft three (34) is made of plastic material and is hollow inside. The outer side of the rotating shaft three (34) has fan blades for driving the lubricating oil to splash. The supporting blocks two (341) at both ends are also made of plastic material and are also hollow inside.

7. The gearbox with lubrication control mechanism according to claim 2, characterized in that: A second support shaft (342) is provided at the upper end of the second support block (341), and the second support shaft (342) passes through the first support block (331) upwards and extends upwards out of the upper cover (11); A support shaft 1 (332) is installed at the upper end of the support block 1 (331), and the support shaft 1 (332) also extends upward from the upper cover (11). The positions where the support shaft 1 (332) and the support shaft 2 (342) extend upward are sealed.

8. The gearbox with lubrication control mechanism according to claim 7, characterized in that: The second support shaft (342) is in contact with the second support block (341); the upper end of the upper cover (11) is fixed with a second frame rod (343); the upper end of the second frame rod (343) is fixed with a transverse threaded tube (344); the threaded tube (344) is internally threadedly connected with a fastening screw (345); the second support shaft (342) passes through the second frame rod (343) upward, and the fastening screw (345) abuts against the second support shaft (342); The support shaft 1 (332) is fixed to the support block 1 (331); a frame rod 1 (333) is fixed to the upper end of the upper cover (11); a fastening nut (334) is rotatably mounted on the upper end of the frame rod 1 (333); the support shaft 1 (332) penetrates the frame rod 1 (333) and the fastening nut (334) upwards and is threadedly connected to the fastening nut (334).

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