A kind of impact-resistant safety high-pressure gas storage tank

Abstract

The present invention discloses a shock-resistant safety high-pressure gas storage tank, which relates to the technical field of gas storage tanks, including a high-pressure tank body, wherein three support columns are fixedly arranged at the bottom of the high-pressure tank body, and the feature is that a plurality of impact dispersion mechanisms are arranged on the outer wall of the high-pressure tank body. The present invention realizes that when a force-bearing area is small, the buffer plate performs preliminary buffering while connecting adjacent buffer boxes, thereby playing a double buffering role, and by docking adjacent buffer boxes, the impact force is dispersed to multiple second springs, the single-point force is dispersed, and the tank body is prevented from being ruptured at a single point, and when a large-area impact force is received, more first springs will disperse the impact force, thereby ensuring the safety of the tank body and adapting to various types and sizes of impact forces.

Description

Technical Field

[0001] The invention relates to the technical field of gas storage tanks, in particular to an impact-resistant safety high-pressure gas storage tank. Background Art

[0002] A gas tank is a device specially used to store gas. It can also stabilize the system pressure. According to the difference in the pressure that the gas tank can withstand, it can be divided into high-pressure gas tanks and normal-pressure gas tanks. Among them, a high-pressure gas tank refers to a device that uses engineering gas to suppress compression and stores gas in a steel or alloy container. This type of tank generally has a pressure regulation and automatic control system. This ensures that the gas will not leak due to external factors, cause environmental pollution, or threaten the safety of the user when in use.

[0003] The utility model patent with patent number CN220817414U discloses a high-pressure gas storage tank, including a tank body, a fixing ring, a rotating plate, a roller, a protective component and a fixing component, wherein the fixing ring is installed at the bottom of the tank body, and a plurality of rotating rings are evenly distributed on the fixing ring, the outer side of the rotating ring and one end of the rotating plate are fixedly installed, and a roller is installed on the other end of the rotating plate, and the number of protective components is multiple, and the plurality of protective components are evenly installed on the outer side of the tank body, and the fixing component is arranged at the lower part of the tank body, wherein the protective component includes an anti-collision shell and an impact sensor, a plurality of anti-collision shells are evenly distributed on the outside of the tank body, an impact sensor is installed inside the anti-collision shell, and an airbag is installed in the anti-collision shell, a mounting seat is installed at the bottom of the tank body, a plurality of support frames are arranged at the bottom of the mounting seat, and the plurality of support frames are evenly distributed at the bottom of the tank body, and the above technical scheme solves the problems of the gas storage tank being difficult to move and having weak protection in the prior art.

[0004] The above-mentioned device is evenly distributed with multiple anti-collision shells on the outside of the tank body, and impact sensors are installed inside the anti-collision shells. In addition, an airbag is installed in the anti-collision shell to reduce the impact force on the high-pressure gas storage tank. However, since the outer wall of the high-pressure tank body is exposed to the external environment for a long time, there are many uncertain factors. It is easy for the high-pressure tank body to be deformed by collision impact, and since the instantaneous speed of the collision impact is extremely fast or the single-point impact force is applied, the safety valve cannot release the gas in time to reduce the air pressure in the tank, resulting in the explosion of the high-pressure tank body, which poses a huge safety hazard to the surrounding staff. Even if the impact force range of the outer wall of the high-pressure tank body is large, it will cause the high-pressure tank body to dent, affecting the amount of high-pressure gas stored in the high-pressure tank body, which will not only reduce the service life of the high-pressure tank body, but also cause leakage of the high-pressure tank body in severe cases. Summary of the invention

[0005] The technical solution of the present invention aims at the technical problem that the existing technical solution is too single, and provides a solution that is significantly different from the existing technology. The specific purpose of the present invention is to provide an impact-resistant and safe high-pressure gas storage tank to solve the problems raised in the above background technology.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: an impact-resistant safety high-pressure gas storage tank, comprising a high-pressure tank body, three supporting columns are fixedly arranged at the bottom of the high-pressure tank body, a plurality of dispersed impact mechanisms are arranged on the outer wall of the high-pressure tank body, a valve seat is fixedly arranged on the top of the high-pressure tank body, a conical cylinder is fixedly arranged on the inner side wall of the valve seat, a protective sleeve is fixedly arranged on the top of the valve seat, a mounting cylinder is fixedly arranged on the top of the protective sleeve, a valve disc is plugged on the top of the conical cylinder, an L-shaped fixing rod is fixedly arranged on the top of the mounting cylinder, a threaded rod is fixedly arranged on one end of the L-shaped fixing rod, a nut is threadedly sleeved on the threaded rod, an adjusting mechanism is fixedly arranged at the bottom of the nut, the adjusting mechanism comprises a disc and an adjusting assembly, the disc is rotatably arranged at the bottom of the nut, a rotating sleeve is fixedly arranged on the top of the nut, the adjusting assembly is fixedly connected to the side wall of the disc, a pressure spring is arranged at the bottom of the disc, a pressure relief mechanism is fixedly arranged on the top of each of the dispersed impact mechanisms, and an air outlet is arranged on the side wall of the mounting cylinder.

[0007] Preferably, the bottom of the valve disc and the bottom of the conical cylinder are both provided with sealing rings, and the bottom of the valve disc and the top of the conical cylinder are sealed and plugged with each other.

[0008] Preferably, each of the dispersed impact mechanisms includes a buffer plate, a buffer box, three first springs, a first wedge block, a plug-in plate, two second wedge blocks, a third wedge block, a plug-in slot, a limit frame and two second springs. The two second springs are fixedly arranged on the side wall of the high-pressure tank body, the buffer box is fixedly arranged on the ends of the two second springs, the three first springs are fixedly arranged inside the buffer box, the buffer plate is fixedly arranged on the end of the first spring, the two second wedge blocks are fixedly arranged on one side wall of the buffer plate close to the buffer box, the first wedge block is plug-in arranged on the inner side wall of the buffer box, the plug-in plate is fixedly arranged on the side wall of the first wedge block away from the buffer box, the third wedge block is plug-in arranged on the other side wall of the buffer box, the plug-in slot is arranged on the side wall of the third wedge block, and the limit frame is fixedly arranged on one side wall of the buffer plate.

[0009] Preferably, each of the plug-in plates is adapted to the corresponding plug-in slot, and each of the second wedge-shaped blocks is abutted against the corresponding first wedge-shaped block or the third wedge-shaped block.

[0010] Preferably, each of the pressure relief mechanisms includes an L-shaped rod, a top rod, a rotating shaft and a support plate, the support plate is fixedly arranged at the bottom of the mounting tube, the rotating shaft is rotatably arranged at the top of the support plate, the top rod is fixedly arranged on the rotating shaft, and the L-shaped rod is fixedly arranged on the top of the corresponding buffer box.

[0011] Preferably, each of the adjustment components comprises two L-shaped adjustment rods, a telescopic rod and a resistance column, one end of the two L-shaped adjustment rods is fixedly arranged on the side wall of the disc, the telescopic rod is fixedly arranged on the end of the top rod, and the resistance column is fixedly arranged on the side wall of the telescopic rod.

[0012] Preferably, each end of the L-shaped adjustment rod is provided with a first inclined surface, and a plurality of the first inclined surfaces are in abutment with corresponding abutment columns.

[0013] Preferably, each end of the telescopic rod is provided with a second inclined surface, and each end of the L-shaped rod is provided with a third inclined surface, and each of the third inclined surfaces is in abutment with and fits with the corresponding second inclined surface.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The present invention realizes that when a force-bearing area is small, the buffer plate performs preliminary buffering while connecting adjacent buffer boxes through the arrangement of a buffer plate, a buffer box, three first springs, a first wedge block, a plug-in plate, two second wedge blocks, a third wedge block, a plug-in slot, a limit frame and two second springs, so as to achieve a double buffering effect. Moreover, by docking adjacent buffer boxes, the impact force is dispersed to multiple second springs, the single-point force is dispersed, and the single-point rupture of the tank body is avoided. Moreover, when a large-area impact force is applied, more first springs will disperse the impact force, thereby ensuring the safety of the tank body, adapting to various types of impact forces, and increasing the service life of the tank body.

[0016] (2) The present invention realizes that when the impact force exceeds the buffering limit of the first spring and the second spring together, the safety valve can be automatically depressurized by the arrangement of the L-shaped rod, the push rod, the rotating shaft and the support plate, so as to avoid the situation where the safety valve fails to release pressure due to the instantaneous excessive impact force. In addition, the pressure relief operation is separately arranged, and the normal operation of the pressure relief valve is not affected during normal use. The whole device does not require manual supervision, has a high degree of automation and is worthy of promotion. In addition, the arrangement of the L-shaped adjusting rod, the telescopic rod and the abutment column realizes that as the maximum gas storage pressure value of the valve increases, the length of the corresponding push rod increases accordingly, thereby increasing the torque for prying the push rod during pressure relief, thereby ensuring that normal pressure relief can be guaranteed regardless of the maximum value of the gas storage pressure inside the tank body, thereby ensuring the safety of the tank body and eliminating the safety hazard of the surrounding staff. No additional operation or adjustment is required, which is convenient and quick. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0018] Figure 2 It is a front cross-sectional structural schematic diagram of the dispersed impact mechanism of the present invention;

[0019] Figure 3 It is a schematic diagram of the back structure of the dispersed impact mechanism of the present invention;

[0020] Figure 4 for Figure 3 Enlarged view of point A in the middle;

[0021] Figure 5 for Figure 3 Enlarged view of point B in the middle;

[0022] Figure 6 It is a schematic diagram of the cross-sectional structure of the installation tube of the present invention;

[0023] Figure 7 It is a schematic diagram of the overall structure of the regulating mechanism of the present invention;

[0024] Figure 8 for Figure 7 Enlarged view of center C.

[0025] In the figure: 1. high-pressure tank; 2. support column; 3. valve seat; 4. impact dispersion mechanism; 41. buffer plate; 42. buffer box; 43. first spring; 44. first wedge block; 45. plug-in plate; 46. second wedge block; 47. third wedge block; 48. plug-in slot; 49. limit frame; 410. second spring; 5. pressure relief mechanism; 51. L-shaped rod; 52. push rod; 53. rotating shaft; 54. support plate; 6. adjustment mechanism; 61. disc; 62. L-shaped adjustment rod; 63. telescopic rod; 64. resistance column; 7. air outlet; 8. mounting tube; 9. threaded rod; 10. rotating sleeve; 11. nut; 13. protective sleeve; 14. conical tube; 15. valve disc; 16. pressure spring; 17. L-shaped fixing rod. DETAILED DESCRIPTION

[0026] 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.

[0027] See also Figure 1-8An embodiment of the present invention is as follows: an impact-resistant safety high-pressure gas storage tank comprises a high-pressure tank body 1, three support columns 2 are fixedly arranged at the bottom of the high-pressure tank body 1, a plurality of impact dispersion mechanisms 4 are arranged on the outer wall of the high-pressure tank body 1, a valve seat 3 is fixedly arranged on the top of the high-pressure tank body 1, a conical cylinder 14 is fixedly arranged on the inner wall of the valve seat 3, a protective sleeve 13 is fixedly arranged on the top of the valve seat 3, a mounting cylinder 8 is fixedly arranged on the top of the protective sleeve 13, a valve disc 15 is inserted on the top of the conical cylinder 14, and an L-shaped fixing rod 17 is fixedly arranged on the top of the mounting cylinder 8 A threaded rod 9 is fixedly provided at one end of the L-shaped fixing rod 17, a nut 11 is threadedly sleeved on the threaded rod 9, an adjusting mechanism 6 is fixedly provided at the bottom of the nut 11, the adjusting mechanism 6 comprises a disc 61 and an adjusting assembly, the disc 61 is rotatably provided at the bottom of the nut 11, a rotating sleeve 10 is fixedly provided at the top of the nut 11, the adjusting assembly is fixedly connected to the side wall of the disc 61, a pressure spring 16 is provided at the bottom of the disc 61, a pressure relief mechanism 5 is fixedly provided at the top of each of the dispersed impact mechanisms 4, and an air outlet 7 is provided on the side wall of the mounting tube 8. First, when the tank body is subjected to a relatively small impact force, this impact force will act on the corresponding dispersion impact mechanism 4, which will automatically connect with the adjacent dispersion impact mechanism 4 through the buffer mechanism to disperse and buffer the impact force. When the tank body is subjected to a relatively large impact force, this impact force will drive the dispersion impact mechanism 4 to start, and the dispersion impact mechanism 4 will synchronously drive the pressure relief mechanism 5 to work, so as to relieve the pressure of the high-pressure tank body 1 to avoid its explosion, and synchronously drive the nut 11 to rotate when the rotating sleeve 10 is rotated, so that the rotation of the nut 11 drives the disc 61 to move downward, and the downward movement of the disc 61 squeezes the pressure spring 16, thereby increasing the pressure on the valve disc 15, thereby adjusting the maximum pressure of the gas that can be stored in the high-pressure tank, and when the nut 11 moves downward and drives the disc 61 to move downward, it will synchronously drive the adjusting mechanism 6 to work, so as to ensure that the pressure relief mechanism 5 works normally at all times to avoid the situation where the pressure is too high and cannot be relieved.

[0028] Specifically, sealing rings are provided at the bottom of the valve disc 15 and the bottom of the conical cylinder 14 , and the bottom of the valve disc 15 and the top of the conical cylinder 14 are sealed and plugged with each other.

[0029] Specifically, each of the dispersed impact mechanisms 4 includes a buffer plate 41, a buffer box 42, three first springs 43, a first wedge block 44, a plug-in plate 45, two second wedge blocks 46, a third wedge block 47, a plug-in groove 48, a limit frame 49 and two second springs 410. The two second springs 410 are fixedly arranged on the side wall of the high-pressure tank body 1, the buffer box 42 is fixedly arranged on the ends of the two second springs 410, the three first springs 43 are fixedly arranged inside the buffer box 42, the buffer plate 41 is fixedly arranged on the end of the first spring 43, the two second wedge blocks 46 are fixedly arranged on a side wall of the buffer plate 41 close to the buffer box 42, the first wedge block 44 is plugged into the inner side wall of the buffer box 42, the plug-in plate 45 is fixedly arranged on the side wall of the first wedge block 44 away from the buffer box 42, the third wedge block 47 is plugged into the other side wall of the buffer box 42, the plug-in groove 48 is arranged on the side wall of the third wedge block 47, and the limit frame 49 is fixedly arranged on one side wall of the buffer plate 41. The impact on the buffer plate 41 drives the second wedge block 46 to move synchronously, and the second wedge block 46 moves to resist the corresponding first wedge block 44 and the third wedge block 47 to extend synchronously, and the first wedge block 44 and the second wedge block 46 extend to dock with the corresponding plug-in plate 45 and the plug-in slot 48, and when the impact force is too large, the buffer plate 41 moves to the maximum distance to drive the buffer box 42 to move synchronously toward the tank body, and the second spring 410 on the back of the buffer box 42 plays a role in buffering the impact force; when the impact with a small force area is achieved, the buffer plate 41 performs preliminary buffering while connecting the adjacent buffer boxes 42, thereby playing a double buffering role, and by docking the adjacent buffer boxes 42, the impact force is dispersed to multiple second springs 410, dispersing the single-point force to avoid single-point rupture of the tank body, and when subjected to a large-area impact force, there will be more first springs 43 to disperse the impact force, thereby ensuring the safety of the tank body, adapting to various types of impact forces, and increasing the service life of the tank body.

[0030] Specifically, each of the plug-in plates 45 is matched with the corresponding plug-in slot 48 , and each of the second wedge-shaped blocks 46 is abutted against and matched with the corresponding first wedge-shaped block 44 or third wedge-shaped block 47 .

[0031] Specifically, each of the pressure relief mechanisms 5 includes an L-shaped rod 51, a push rod 52, a rotating shaft 53 and a support plate 54. The support plate 54 is fixedly arranged at the bottom of the mounting tube 8, the rotating shaft 53 is rotatably arranged at the top of the support plate 54, the push rod 52 is fixedly arranged on the rotating shaft 53, and the L-shaped rod 51 is fixedly arranged at the top of the corresponding buffer box 42. The L-shaped rod 51 is driven to move by the movement of the buffer box 42, and the L-shaped rod 51 moves against the top of the corresponding telescopic rod 63, so that the telescopic rod 63 drives the push rod 52 to rotate around the rotating shaft 53, so that the end of the rotating shaft 53 close to the valve disc 15 is tilted, and the valve disc 15 is lifted, so as to relieve the pressure inside the tank body; it is realized that when the impact force has exceeded the buffer limit of the first spring 43 and the second spring 410 together, the safety valve can be automatically relieved, so as to avoid the situation that the safety valve fails to relieve pressure due to the instantaneous excessive impact force, and the pressure relief operation set separately will not affect the normal operation of the pressure relief valve during normal use. The whole device does not need manual supervision, has a high degree of automation, and is worthy of promotion.

[0032] Specifically, each of the adjustment components includes two L-shaped adjustment rods 62, a telescopic rod 63 and a resistance column 64. One end of the two L-shaped adjustment rods 62 is fixedly set on the side wall of the disc 61, the telescopic rod 63 is fixedly set on the end of the top rod 52, and the resistance column 64 is fixedly set on the side wall of the telescopic rod 63. The L-shaped adjustment rod 62 is driven downward by the disc 61, and the L-shaped adjustment rod 62 is driven downward to drive the resistance column 64 to move toward the L-shaped adjustment rod 62; as the maximum gas storage pressure value of the valve increases, the length of the corresponding top rod 52 increases accordingly, thereby increasing the torque for prying the top rod 52 during pressure relief, thereby ensuring that no matter how much the maximum pressure of the gas stored in the tank is, normal pressure relief can be guaranteed, ensuring the safety of the tank, eliminating the safety hazards of the surrounding staff, and no additional operation and adjustment are required, which is convenient and quick.

[0033] Specifically, each end of the L-shaped adjustment rod 62 is provided with a first inclined surface, and a plurality of the first inclined surfaces are in abutment with the corresponding abutment columns 64 .

[0034] Specifically, each end of the telescopic rod 63 is provided with a second inclined surface, and each end of the L-shaped rod 51 is provided with a third inclined surface, and each of the third inclined surfaces is in abutment with and cooperates with the corresponding second inclined surface.

[0035] Working principle: First, when the tank body is subjected to a small impact force, the buffer plate 41 is impacted, thereby driving the second wedge block 46 to move synchronously, and the second wedge block 46 moves to contact the corresponding first wedge block 44 and the third wedge block 47 to extend synchronously, and the first wedge block 44 and the second wedge block 46 extend to connect with the corresponding plug-in plate 45 and the plug-in slot 48, and when the impact force is too large, the buffer plate 41 moves to the maximum distance to drive the buffer box 42 to move synchronously toward the tank body, and the second spring 410 on the back of the buffer box 42 plays a role in buffering the impact force, and synchronously drives the L-shaped rod 51 to move through the movement of the buffer box 42, and the L-shaped rod 51 moves to contact the top of the corresponding telescopic rod 63, so that the telescopic rod 63 drives the top rod 52 to rotate around the rotating shaft 53, so that The end of the rotating shaft 53 close to the valve disc 15 is tilted up, and the valve disc 15 is lifted up, thereby relieving the pressure inside the tank body, and synchronously, the rotating sleeve 10 drives the nut 11 to rotate, so that the rotation of the nut 11 drives the disc 61 to move downward, and the disc 61 moves downward to squeeze the pressure spring 16, so that the pressure on the valve disc 15 increases, thereby adjusting the maximum pressure of the gas that can be stored in the high-pressure tank. The downward movement of the disc 61 drives the L-shaped adjusting rod 62 to move downward, and the downward movement of the L-shaped adjusting rod 62 drives the resistance column 64 to move toward the L-shaped adjusting rod 62. The extension of the telescopic rod 63 increases the torque of the push rod 52 accordingly, so that the force of the L-shaped rod 51 against the telescopic rod 63 to drive the push rod 52 to rotate becomes smaller, thereby avoiding the situation where the pressure is too high and cannot be relieved.

Claims

1. An impact-resistant safety high-pressure gas storage tank, comprising a high-pressure tank body (1), wherein three support columns (2) are fixedly arranged at the bottom of the high-pressure tank body (1), characterized in that: The outer wall of the high-pressure tank body (1) is provided with a plurality of impact dispersion mechanisms (4); a valve seat (3) is fixedly provided on the top of the high-pressure tank body (1); a conical cylinder (14) is fixedly provided on the inner wall of the valve seat (3); a protective sleeve (13) is fixedly provided on the top of the valve seat (3); a mounting cylinder (8) is fixedly provided on the top of the protective sleeve (13); a valve disc (15) is inserted and provided on the top of the conical cylinder (14); an L-shaped fixing rod (17) is fixedly provided on the top of the mounting cylinder (8); a threaded rod (9) is fixedly provided on one end of the L-shaped fixing rod (17); a nut (11) is threadedly provided on the threaded rod (9); an adjusting mechanism (6) is fixedly provided on the bottom of the nut (11); the adjusting mechanism (6) includes The invention comprises a disc (61) and an adjusting assembly, wherein the disc (61) is rotatably arranged at the bottom of a nut (11), a rotating sleeve (10) is fixedly arranged at the top of the nut (11), the adjusting assembly is fixedly connected to the side wall of the disc (61), a pressure spring (16) is arranged at the bottom of the disc (61), a pressure relief mechanism (5) is fixedly arranged at the top of each of the dispersed impact mechanisms (4), an air outlet (7) is arranged at the side wall of the mounting tube (8), and each of the dispersed impact mechanisms (4) comprises a buffer plate (41), a buffer box (42), three first springs (43), a first wedge block (44), a plug-in plate (45), two second wedge blocks (46), a third wedge block (47), a plug-in slot (48), a limit frame ( 49) and two second springs (410), the two second springs (410) are fixedly arranged on the side wall of the high-pressure tank body (1), the buffer box (42) is fixedly arranged at the ends of the two second springs (410), the three first springs (43) are fixedly arranged inside the buffer box (42), the buffer plate (41) is fixedly arranged at the ends of the first springs (43), the two second wedge blocks (46) are fixedly arranged on a side wall of the buffer plate (41) close to the buffer box (42), the first wedge block (44) is plugged into the inner side wall of the buffer box (42), the plug-in plate (45) is fixedly arranged on the side wall of the first wedge block (44) away from the buffer box (42), and the third wedge block (47) is plugged into The other side wall of the buffer box (42), the plug-in slot (48) is arranged on the side wall of the third wedge block (47), the limit frame (49) is fixedly arranged on one side wall of the buffer plate (41), each of the pressure relief mechanisms (5) comprises an L-shaped rod (51), a top rod (52), a rotating shaft (53) and a support plate (54), the support plate (54) is fixedly arranged on the bottom of the mounting tube (8), the rotating shaft (53) is rotatably arranged on the top of the support plate (54), the top rod (52) is fixedly arranged on the rotating shaft (53), the L-shaped rod (51) is fixedly arranged on the top of the corresponding buffer box (42), and each of the adjustment components comprises two L-shaped adjustment rods (62), a telescopic rod (63) and a contact column (64),One end of the two L-shaped adjustment rods (62) is fixedly arranged on the side wall of the disc (61), the telescopic rod (63) is fixedly arranged on the end of the top rod (52), and the abutment column (64) is fixedly arranged on the side wall of the telescopic rod (63).

2. The impact-resistant safety high-pressure gas storage tank according to claim 1, characterized in that: The bottom of the valve disc (15) and the bottom of the conical cylinder (14) are both provided with sealing rings, and the bottom of the valve disc (15) and the top of the conical cylinder (14) are sealed and plugged with each other.

3. The impact-resistant safety high-pressure gas storage tank according to claim 1, characterized in that: Each of the plug-in plates (45) is mutually matched with a corresponding plug-in slot (48), and each of the second wedge-shaped blocks (46) is in abutment with a corresponding first wedge-shaped block (44) or a third wedge-shaped block (47).

4. The impact-resistant safety high-pressure gas storage tank according to claim 1, characterized in that: Each of the L-shaped adjustment rods (62) is provided with a first inclined surface at the end thereof, and a plurality of the first inclined surfaces are in abutment with corresponding abutment columns (64).

5. The impact-resistant safety high-pressure gas storage tank according to claim 1, characterized in that: The end of each telescopic rod (63) is provided with a second inclined surface, and the end of each L-shaped rod (51) is provided with a third inclined surface, and each third inclined surface is in abutment with the corresponding second inclined surface.

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