Liftable kiln car
By designing a liftable kiln car and utilizing the coordination of the lifting frame and the rocking rod, the problem of temperature unevenness caused by inconsistent kiln car heights was solved, the height consistency adjustment of the refractory bricks on the kiln car platform was achieved, and the firing temperature uniformity of the tunnel kiln was improved.
Patent Information
- Application Number
- CN202422850649.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-22
- Publication Date
- 2025-10-03
- Estimated Expiration
- 2034-11-22
AI Technical Summary
The inconsistent height of the kiln car in the tunnel kiln leads to temperature differences in the local firing temperature, which affects the firing quality of the refractory bricks.
A liftable kiln car is designed. The height of the kiln car can be adjusted through the cooperation of a lifting frame, a rocking handle and a rocking rod, thereby ensuring the height consistency of the refractory bricks on the kiln car platform.
It effectively prevents local firing temperature differences caused by inconsistent cross-section heights in the tunnel kiln and improves the firing temperature uniformity of refractory bricks on the kiln car.
Smart Images
Figure CN223412493U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of liftable kiln cars, and in particular relates to a liftable kiln car. Background Art
[0002] A tunnel kiln is a modern, continuous-firing, thermally-engineered furnace constructed of refractory, insulation, and building materials, equipped with a kiln car and other transport vehicles. The kiln car is a key conveying device for tunnel kilns, primarily used to stack refractory bricks and, through a traction mechanism, to move the kiln car through the closed tunnel kiln during high-temperature firing. During the firing of refractory bricks, multiple kiln cars are positioned within the tunnel kiln. After the refractory bricks have been fired, the kiln cars are pulled out of the tunnel kiln one by one by a traction mechanism for cooling.
[0003] In the tunnel kiln firing process, the uniformity of the firing temperature directly affects the firing quality of the refractory bricks on the kiln car. Because multiple kiln cars are placed in the tunnel kiln, refractory bricks of different specifications may be stacked on the kiln cars to improve firing thermal efficiency. Due to the different sizes of refractory bricks, when stacked on the kiln cars, the stacking heights of the refractory bricks on the kiln cars will inevitably be different. This will cause the two kiln cars to be at different heights in the tunnel kiln. The two kiln cars with different cross-sections (kiln car heights) will inevitably lead to localized temperature differences in the tunnel kiln, reducing the uniformity of the firing temperature within the tunnel kiln. Based on the above-mentioned shortcomings of the prior art, the inventors have developed a liftable kiln car that can address the technical problems existing in the prior art. Utility Model Content
[0004] To address the aforementioned technical issues, this utility model provides a liftable kiln car with a simple structure and scientifically designed design. This allows the car to be raised and lowered in the tunnel kiln after stacking refractory bricks. This liftable kiln car solves the problem of localized firing temperature differences between kiln cars with different cross-sections (kiln car heights), which can reduce firing temperature uniformity within the tunnel kiln.
[0005] The technical solution adopted by the present invention is: a liftable kiln car, comprising a kiln car platform 1, a refractory brick layer 2, and a surrounding plate 3; the kiln car platform 1 is fixedly arranged at the upper position of the refractory brick layer 2, and the surrounding plate 3 is fixedly arranged around the bottom of the refractory brick layer 2, and the height of the surrounding plate 3 is lower than the height of the refractory brick layer 2; the retaining edge 4 is fixedly arranged on the inner edge around the upper part of the skirt 5, and the skirt 5 is fixedly sleeved on the outside around the steel frame 6, and the refractory brick layer 2 is fixedly built on the upper part of the steel frame 6; the lifting frame 7 is fixedly welded to the bottom position of the steel frame 6, and the lifting frame 7 is fixedly arranged at the bottom of the steel frame 6 in a left-right symmetrical manner; four rolling wheel groups 8 are fixedly arranged, and the rolling wheel group 8 is fixedly arranged at the front and rear bottom positions of each lifting frame 7; the shaking handle 9 is fixedly arranged at the left end position of the shaking rod 10, and the shaking rod 10 is horizontally installed in the middle position of the left-right symmetrical lifting frame 7.
[0006] The enclosure 3 is a hollow square shape, and the area of the kiln car platform 1 is equal to the area of the enclosure 3; the refractory bricks used in the refractory brick layer 2 are lightweight refractory bricks, and the retaining edge 4 is a hollow square shape, and the area of the retaining edge 4 is smaller than that of the skirt 5.
[0007] The lifting frame 7 includes a double hinged plate 71, which is symmetrically arranged front to back, and a single hinged plate 72 is symmetrically installed front to back in the middle position of the upper part of the double hinged plate 71, and is fixed and hinged by a second connecting rod 75 passing through the upper part of the double hinged plate 71 and the lower part of the single hinged plate 72; a reinforcement block 73 is installed at the middle position of the bottom of the double hinged plate 71, and the front and rear ends of the connecting rod 1 74 pass through the lower part of the double hinged plate 71 and the reinforcement block 73 for hinged fixation; a double reinforcement block 77 is symmetrically arranged front to back on the upper part of the single hinged plate 72, and a connecting plate 78 is arranged on the outside of the double reinforcement block 77, and the front and rear ends of the connecting rod 3 76 pass through the double reinforcement block 77, the single hinged plate 72, and the connecting plate 78 for hinged fixation; the upper end surfaces of the double reinforcement block 77, the single hinged plate 72, and the connecting plate 78 are fixed and welded to the bottom of the steel frame 6; a lifting body 79 is installed in the middle position of the second connecting rod 75, and a thread hole 710 is opened in the center of the side of the lifting body 79.
[0008] The rolling wheel assembly 8 includes a fixed plate 81, which is symmetrically arranged on the bottom outer side of the double hinged plate 71 in front and back directions. The wheel axle 82 is fixedly arranged on the left outer side of the fixed plate 81. The mounting plate 83 is fixedly arranged on the wheel axle 82. The wheel axle 82 passes through the center of the mounting plate 83 and extends to the outer side of the mounting plate 83. The roller 84 is installed on the outer side of the mounting plate 83. The axle seat 85 is installed at the outer center position of the roller 84. The fixing nut 86 is tightened and installed on the outer end of the wheel axle 82.
[0009] The rocking rod 10 includes a rocking rod body 101, which is cylindrical. The first external thread 102 is opened near the left end of the rocking rod body 101, and the second external thread 103 is opened at the right end of the rocking rod body 101; the thread lengths of the first external thread 102 and the second external thread 103 are equal.
[0010] The rocking handle 9 is in the shape of a letter "7" and is fixed to the left end of the rocking rod body 101 . The rocking handle 9 and the rocking rod body 101 are vertically fixedly connected.
[0011] The rocking rod body 101 is installed in the thread hole 710 of the left and right symmetrical lifting body 79, the external thread 102 is threadedly engaged with the thread hole 710 of the lifting body 79 on the left, and the external thread 2 103 is threadedly engaged with the thread hole 710 of the lifting body 79 on the right; the external thread 102 is a clockwise thread, and the external thread 2 103 is a counterclockwise thread.
[0012] The working process of this liftable kiln car is as follows: after the refractory bricks are stacked on the kiln car platform 1, the liftable kiln car is transported to the entrance of the tunnel kiln through the traction mechanism of the tunnel kiln. When the height of the refractory bricks stacked on the liftable kiln car is too high or too low, the liftable kiln car can be lowered. When the height of the liftable kiln car needs to be lowered, the operator shakes the handle 9 to rotate forward, driving the rocker body 101 to rotate forward, and the external thread 102 on the rocker body 101 engages with the threaded hole 710 in the lifting body 79 on the lifting frame 7 to rotate and match, so that the lifting body 79 on the left side of the lifting frame 7 moves to the right, and at the same time the external thread 203 engages with the threaded hole 710 in the lifting body 79 on the lifting frame 7 to rotate and match, so that the lifting body 79 on the left side of the lifting frame 7 moves to the right. The meshing and rotating engagement of the two hinge plates 71 and 72 causes the lifting member 79 on the right side of the lifting frame 7 to move leftward. Simultaneously, as the lifting members 79 on the left and right sides of the lifting frame 7 move toward the center of the rocking lever body 101, the connecting rods 75 of the left and right lifting frames 7 are driven to move toward the center of the rocking lever body 101. At this point, through the articulated action of the double hinged plate 71 and the single hinged plate 72 (and simultaneously under the weight of the kiln car platform 1, refractory brick layer 2, enclosure 3, rib 4, skirt 5, steel frame 6, and refractory bricks), the single hinged plate 72 folds downward with the connecting rod 75 as the hinge center, thereby lowering the movable kiln car and the refractory bricks on the kiln car platform 1. To raise the movable kiln car and the refractory bricks on the kiln car platform 1, the reverse of the lowering action of the movable kiln car is performed. The operator rotates the rocking handle 9 forward or reversely, and utilizes the forward or reverse rotation of the rocking handle 9 to drive the rocking rod 10 to rotate forward or reverse, thereby driving the lifting body 79 of the lifting frame 7 and the connecting rod 2 75 to move toward or away from each other along the rocking rod body 101, and finally adjusting the height of the liftable kiln car and the refractory bricks on the kiln car platform, and finally adjusting the height difference between the individual liftable kiln cars and other liftable kiln cars to maintain the same height as the others, and transporting the liftable kiln cars and refractory bricks with the same height to the tunnel kiln in sequence through the traction mechanism, effectively preventing the problem of temperature difference in local firing temperature due to inconsistent cross-sectional height in the tunnel kiln.
[0013] The beneficial effects of the utility model are as follows: through the arrangement of the lifting frame, the rocking handle and the rocking rod, the height of the lifting frame can be raised and lowered, thereby achieving the adaptability and consistency of the height of the stacked refractory bricks on the kiln car platform; the heights of all the liftable kiln cars and refractory bricks in the tunnel kiln are kept consistent, effectively preventing the problem of temperature difference in local firing temperature due to inconsistent cross-sectional heights in the tunnel kiln. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 It is a structural diagram of the utility model;
[0015] Figure 2This is a schematic diagram of the structure of the lifting frame and rolling wheel assembly of the utility model;
[0016] Figure 3 This is a schematic structural diagram of the skirt, steel frame, lifting frame, rocking handle and rocking rod of the present invention;
[0017] Markings in the figure: 1. Kiln car platform, 2. Refractory brick layer, 3. Enclosure, 4. Sidewall, 5. Skirt, 6. Steel frame, 7. Lifting frame, 71. Double hinged plate, 72. Single hinged plate, 73. Reinforcement block, 74. Connecting rod one, 75. Connecting rod two, 76. Connecting rod three, 77. Double reinforcement block, 78. Connecting plate, 79. Lifting body, 710. Thread hole, 8. Rolling wheel set, 81. Fixed plate, 82. Wheel axle, 83. Mounting plate, 84. Roller, 85. Axle seat, 86. Fixing nut, 9. Rocking handle, 10. Rocking rod, 101. Rocking rod body, 102. External thread one, 103. External thread two. DETAILED DESCRIPTION
[0018] The specific implementation of the present invention is further described in detail below with reference to the accompanying drawings.
[0019] The utility model provides a liftable kiln car:
[0020] like Figure 1 As shown, the kiln car platform 1 is fixedly arranged at the upper position of the refractory brick layer 2, and the enclosure 3 is fixedly arranged around the bottom of the refractory brick layer 2, and the height of the enclosure 3 is lower than the height of the refractory brick layer 2; the retaining edge 4 is fixedly arranged on the inner edge around the upper part of the skirt 5, and the skirt 5 is fixedly sleeved on the outside around the steel frame 6, and the refractory brick layer 5 is fixedly built on the upper part of the steel frame 6; the enclosure 3 is a hollow square shape, and the area of the kiln car platform 1 is equal to the area of the enclosure 3; the refractory bricks built in the refractory brick layer 2 are lightweight refractory bricks, and the retaining edge 4 is a hollow square shape, and the area of the retaining edge 4 is smaller than that of the skirt 5.
[0021] The above-mentioned kiln car platform 1 is provided for stacking refractory bricks. The above-mentioned refractory brick layer 2, which is a lightweight refractory brick, can, on the one hand, reduce the weight of the kiln car and prevent the traction mechanism of the kiln car from being overloaded due to the heavy weight of the kiln car; on the other hand, it improves the thermal insulation performance of the kiln car and reduces the heat energy consumption of the refractory bricks on the kiln car. The above-mentioned setting of the enclosure 3 and the side dam 4 can protect the skirt 5 and prevent the upper heat in the tunnel kiln from entering the surrounding of the skirt. The above-mentioned setting of the steel frame 6 can, on the one hand, provide the rigidity of the kiln car and increase the load-bearing capacity of the kiln car; on the other hand, it can effectively prevent the high-temperature deformation of the lifting frame 7, the rolling wheel group 8, the shaking handle 9 and the shaking rod 10 under high-temperature environment.
[0022] like Figure 2As shown, the lifting frame 7 is fixedly arranged at the bottom of the steel frame 6 symmetrically on the left and right sides. The lifting frame 7 includes a double hinged plate 71, which is symmetrically arranged front and back. The single hinged plate 72 is symmetrically installed front and back at the upper middle position of the double hinged plate 71 and is fixedly hinged by a connecting rod 2 75 passing through the upper part of the double hinged plate 71 and the lower part of the single hinged plate 72; the reinforcement block 73 is installed at the bottom middle position of the double hinged plate 71, and the front and rear ends of the connecting rod 1 74 pass through the lower part of the double hinged plate 71 and the reinforcement block respectively. 73 is hinged and fixed; the double reinforcement blocks 77 are symmetrically arranged on the upper part of the single hinge plate 72, and the connecting plate 78 is arranged on the outside of the double reinforcement block 77. The front and rear ends of the connecting rod three 76 pass through the double reinforcement block 77, the single hinge plate 72, and the connecting plate 78 for hinged fixation; the upper end faces of the double reinforcement block 77, the single hinge plate 72, and the connecting plate 78 are fixedly welded to the bottom of the steel frame 6; the lifting body 79 is installed in the middle position of the connecting rod two 75, and a wire hole 710 is opened in the center of the side of the lifting body 79.
[0023] By means of the arrangement of the double hinged plate 71, the single hinged plate 72, the reinforcement block 73, the connecting rod 1 74, the connecting rod 2 75, the connecting rod 3 76, the double reinforcement block 77, the connecting plate 78, the lifting body 79 and the threaded hole 710, when the operator shakes the handle 9 to rotate forward or reverse, driving the shaking rod body 101 to rotate forward or reverse, the external thread 102 on the shaking rod body 101 engages and rotates with the threaded hole 710 in the lifting body 79 on the lifting frame 7, so that the lifting body 79 on the left side of the lifting frame 7 moves to the right or left side, and at the same time, the external thread 2 103 engages and rotates with the threaded hole 710 in the lifting body 79 on the lifting frame 7, so that the lifting body 79 on the right side of the lifting frame 7 moves to the left or right side. When the lifting frame 7 moves to the right, the lifting bodies 79 on the left and right sides of the lifting frame 7 move toward the middle position of the rocking rod body 101 or move outward synchronously, thereby driving the connecting rods 2 75 of the left and right lifting frames 7 to move toward the middle position or the outer position of the rocking rod body 101. At this time, through the hinged action of the double hinged plate 71 and the single hinged plate 72, and under the weight of the kiln car platform 1, the refractory brick layer 2, the enclosure 3, the retaining wall 4, the skirt 5, the steel frame 6 and the refractory brick blanks, the single hinged plate 72 folds downward or unfolds upward with the connecting rod 2 75 as the hinge center, thereby realizing the lifting action of the elevator 7 and finally realizing the lifting and lowering adjustment of the refractory brick blanks on the kiln car platform 1.
[0024] like Figure 1 、 2As shown in Figure 3, four rolling wheel groups 8 are fixedly provided, and the rolling wheel groups 8 are fixedly provided at the front and rear bottom positions of each lifting frame 7; the rolling wheel group 8 includes a fixing plate 81, which is symmetrically arranged on the bottom outer side of the double-hinged plate 71 in front and back, a wheel axle 82 is fixedly provided on the left outer side of the fixing plate 81, and a mounting plate 83 is fixed on the wheel axle 82. The wheel axle 82 passes through the center of the mounting plate 83 and extends to the outer side of the mounting plate 83. The roller 84 is installed on the outer side of the mounting plate 83, the axle seat 85 is installed at the outer center position of the roller 84, and the fixing nut 86 is tightened and installed on the outer end of the wheel axle 82.
[0025] The arrangement of the four rolling wheel groups 8 provides rolling support for the refractory bricks on the kiln car platform 1 .
[0026] like Figure 1 As shown in Figure 3, the rocking handle 9 is fixedly arranged at the left end position of the rocking rod 10, and the rocking rod 10 is horizontally installed in the middle position of the bilaterally symmetrical lifting frame 7; the rocking rod 10 includes a rocking rod body 101, the rocking rod body 101 is cylindrical, the external thread 102 is opened near the left end position of the rocking rod body 101, and the external thread 2 103 is opened at the right end position of the rocking rod body 101; the thread lengths of the external thread 102 and the external thread 2 103 are equal; the rocking rod body 101 is installed in the thread hole 710 of the bilaterally symmetrical lifting body 79, the external thread 102 is threadedly engaged with the thread hole 710 of the lifting body 79 on the left, and the external thread 2 103 is threadedly engaged with the thread hole 710 of the lifting body 79 on the right; the external thread 102 is a clockwise thread, and the external thread 2 103 is a counterclockwise thread.
[0027] By configuring the rocking handle 9 and the rocking rod 10 as described above, when the operator rotates the rocking handle 9 , the rocking rod 10 can be driven to rotate in a forward or reverse direction.
[0028] By providing the external thread 102 and the external thread 2 103 on the rocking rod body 101, the thread hole 710 provided in the lifting body 79 of the lifting frame 7 on the left and the thread hole 710 provided in the lifting body 79 of the lifting frame 7 on the right are engaged and rotated together, so that the lifting body 79 of the lifting frame 7 on the left and the lifting body 79 of the lifting frame 7 on the right can move synchronously towards or against each other, thereby finally realizing the lifting and lowering adjustment of the height of the liftable kiln car.
[0029] like Figure 1-3As shown, the working process of this liftable kiln car is as follows: after the refractory bricks are stacked on the kiln car platform 1, the liftable kiln car is transported to the entrance of the tunnel kiln through the traction mechanism of the tunnel kiln. For the liftable kiln car whose stacked refractory bricks are too high or too low; when it is necessary to lower the height of the liftable kiln car, the operator shakes the handle 9 to rotate forward, driving the rocker body 101 to rotate forward, and the external thread 102 on the rocker body 101 engages with the thread hole 710 in the lifting body 79 on the lifting frame 7 to rotate and cooperate, so that the lifting body 79 on the left side of the lifting frame 7 moves to the right, and at the same time the external thread 203 engages with the thread hole 710 in the lifting body 79 on the lifting frame 7. The engagement and rotation of the holes 710 cause the lifting body 79 on the right side of the lifting frame 7 to move leftward. As the lifting bodies 79 on the left and right sides of the lifting frames 7 move toward the center of the rocking lever body 101, they also drive the connecting rods 75 of the left and right lifting frames 7 to move toward the center of the rocking lever body 101. At this point, through the articulated action of the double hinged plate 71 and the single hinged plate 72 (and under the weight of the kiln car platform 1, refractory brick layer 2, enclosure 3, rib 4, skirt 5, steel frame 6, and refractory bricks), the single hinged plate 72 folds downward with the connecting rod 75 as the hinge center, thereby lowering the movable kiln car and the refractory bricks on the kiln car platform 1. To raise the movable kiln car and the refractory bricks on the kiln car platform 1, the reverse of the lowering action of the movable kiln car is performed. The operator rotates the rocking handle 9 forward or reverse, and utilizes the forward or reverse rotation of the rocking handle 9 to drive the rocking rod 10 to rotate forward or reverse, thereby driving the lifting body 79 of the lifting frame 7 and the second connecting rod 75 to move toward or away from each other along the rocking rod body 101, and finally adjusting the height of the liftable kiln car and the refractory bricks on the kiln car platform, and finally adjusting the height difference between the individual liftable kiln cars and other liftable kiln cars to maintain the overall height consistency; effectively preventing the problem of temperature difference in local firing temperature due to inconsistent cross-sectional height in the tunnel kiln.
[0030] Various modifications to the above-described embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not limited to the embodiments shown herein, but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.
Claims
1. A liftable kiln car, comprising a kiln car platform (1), a refractory brick layer (2), and a panel (3); the kiln car platform (1) is fixedly arranged above the refractory brick layer (2), and is characterized in that: The enclosure (3) is fixedly arranged around the bottom of the refractory brick layer (2), and the height of the enclosure (3) is lower than the height of the refractory brick layer (2); the retaining edge (4) is fixedly arranged on the inner edge around the upper part of the skirt (5), and the skirt (5) is fixedly sleeved on the outer periphery of the steel frame (6), and the refractory brick layer (2) is fixedly built on the upper part of the steel frame (6); the lifting frame (7) is fixedly welded to the bottom position of the steel frame (6), and the lifting frame (7) is fixedly arranged on the bottom of the steel frame (6) in a symmetrical manner; four rolling wheel groups (8) are fixedly arranged, and the rolling wheel groups (8) are fixedly arranged at the front and rear bottom positions of each lifting frame (7); the shaking handle (9) is fixedly arranged at the left end position of the shaking rod (10), and the shaking rod (10) is horizontally installed in the middle position of the lifting frame (7) that is symmetrical on the left and right.
2. The liftable kiln car according to claim 1, characterized in that: The enclosure (3) is in a hollow square shape, and the area of the kiln car platform (1) is equal to the area of the enclosure (3); the refractory bricks used to build the refractory brick layer (2) are lightweight refractory bricks, and the retaining edge (4) is in a hollow square shape, and the area of the retaining edge (4) is smaller than the area of the skirt (5).
3. The liftable kiln car according to claim 1, characterized in that: The lifting frame (7) includes a double hinged plate (71), the double hinged plate (71) is symmetrically arranged front and back, and the single hinged plate (72) is symmetrically installed front and back at the middle position of the upper part of the double hinged plate (71), and is fixed and hinged by a second connecting rod (75) passing through the upper part of the double hinged plate (71) and the lower part of the single hinged plate (72); a reinforcement block (73) is installed at the middle position of the bottom of the double hinged plate (71), and the front and rear ends of the first connecting rod (74) respectively pass through the lower part of the double hinged plate (71) and the reinforcement block (73) for hinged fixation; the double reinforcement block (77 ) are symmetrically arranged on the upper part of the single hinge plate (72) front and back, the connecting plate (78) is arranged on the outside of the double reinforcement block (77), the front and rear ends of the connecting rod three (76) respectively pass through the double reinforcement block (77), the single hinge plate (72), and the connecting plate (78) for hinged fixation; the upper end faces of the double reinforcement block (77), the single hinge plate (72), and the connecting plate (78) are fixedly welded to the bottom of the steel frame (6); the lifting body (79) is installed in the middle position of the connecting rod two (75), and a thread hole (710) is opened in the center of the side of the lifting body (79).
4. The liftable kiln car according to claim 1, characterized in that: The rolling wheel assembly (8) comprises a fixing plate (81) which is symmetrically arranged on the outer side of the bottom of the double hinged plate (71) in a front-to-back manner. The wheel axle (82) is fixedly arranged on the outer side of the left side of the fixing plate (81). The mounting plate (83) is fixedly arranged on the wheel axle (82). The wheel axle (82) passes through the center of the mounting plate (83) and extends to the outer side of the mounting plate (83). The roller (84) is mounted on the outer side of the mounting plate (83). The shaft seat (85) is mounted at the outer center position of the roller (84). The fixing nut (86) is tightened and mounted on the outer end of the wheel axle (82).
5. The liftable kiln car according to claim 1, characterized in that: The rocking rod (10) comprises a rocking rod body (101), the rocking rod body (101) is cylindrical, the first external thread (102) is provided near the left end of the rocking rod body (101), and the second external thread (103) is provided at the right end of the rocking rod body (101); the thread lengths of the first external thread (102) and the second external thread (103) are equal.
6. The liftable kiln car according to claim 1, characterized in that: The shaking handle (9) is in the shape of a letter "7" and is fixed at the left end of the shaking rod body (101). The shaking handle (9) and the shaking rod body (101) are vertically fixedly connected.
7. The liftable kiln car according to claim 5, characterized in that: The rocking rod body (101) is installed in the thread hole (710) of the left and right symmetrical lifting body (79), the external thread 1 (102) is threadedly engaged with the thread hole (710) of the left lifting body (79), and the external thread 2 (103) is threadedly engaged with the thread hole (710) of the right lifting body (79); the external thread 1 (102) is a clockwise thread, and the external thread 2 (103) is a counterclockwise thread.