Automatic distance adjusting mechanism for upper and lower belt conveyors of cowhide fuse machine

Abstract

The utility model belongs to the technical field of cowhide fuse machines, and discloses an automatic distance adjusting mechanism for upper and lower belt conveyors of a cowhide fuse machine, which comprises a support frame, an adjusting mechanism is arranged on the outer side of the support frame, and the adjusting mechanism extends into the support frame; the adjusting mechanism comprises an upper belt conveyor and a lower belt conveyor, the upper belt conveyor is located at the top of the lower belt conveyor, and first motors are fixedly connected to the two sides of the lower belt conveyor. The problems that an existing fuse machine is single in structure and function, the distance between most of upper and lower belt lines cannot be rapidly adjusted according to the use specification of process requirements, the overall flexibility is low, and the applicability is poor, so that the practicability is reduced, the manufacturing cost of products is increased, and the production cost is reduced are solved. And the stability of product output is influenced.

Description

Technical Field

[0001] This application relates to the technical field of cowhide hot melt machines, and more specifically, to an automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine. Background Art

[0002] The hot melt machine transmits ultrasonic energy to the welding area through the upper welding part. Since the acoustic resistance at the welding area, that is, the interface of the two welds, is large, local high temperature will be generated. Also, due to the poor thermal conductivity of plastics, it cannot be dissipated in time for a while and accumulates in the welding area, causing the contact surfaces of the two plastics to melt rapidly. With a certain pressure, they are fused into one body. When the ultrasonic wave stops acting, the pressure is maintained for a few seconds to make it solidify and form, thus forming a strong molecular chain to achieve the purpose of welding, and the welding strength can be close to the strength of the raw material.

[0003] When the existing hot melt machine is performing hot melt work, its structure is relatively simple and its function is relatively single. Since the distance between most upper and lower belt lines cannot be quickly adjusted according to the usage regulations of the process requirements, the overall flexibility is low and the applicability is poor. Therefore, it will not only cause the reduction of practicality and increase the manufacturing cost of products, but also affect the stability of product output, so it does not have good promotion value.

[0004] In order to solve the above problems, this application provides an automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine. Content of the Utility Model

[0005] The automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine provided by this application adopts the following technical solution:

[0006] An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine includes a support frame, and an adjustment mechanism is arranged outside the support frame and extends into the support frame;

[0007] The adjusting mechanism includes an upper belt conveyor and a lower belt conveyor. The upper belt conveyor is located on top of the lower belt conveyor. On both sides of the lower belt conveyor, a first motor is fixedly connected. The two first motors are symmetrically arranged before and after with the midline of the lower belt conveyor as the axis. The output shafts of the two first motors are fixedly connected with rollers. On the outer sides of the two rollers, a first sprocket is fixedly sleeved. On top of the two first sprockets, a second sprocket is provided. On the outer sides of the two first sprockets and the two second sprockets, a chain is sleeved. The two first sprockets and the two second sprockets are respectively driven and connected by the two chains. Inside the two second sprockets, a connecting rod is fixedly embedded. On the outer sides of the two connecting rods, two worm and worm gear lifters are installed. The four worm and worm gear lifters are respectively located on one side of the two second sprockets. On the outer sides of the tops of the four worm and worm gear lifters, a lifter screw mounting bracket is installed. The four lifter screw mounting brackets are respectively fixedly connected to both sides of the upper belt conveyor. On the outer sides of the four lifter screw mounting brackets, an auxiliary structure is provided.

[0008] Further, the four worm and worm gear lifters are respectively installed on both sides of the lower belt conveyor. On the bottoms of the two first motors, a base is installed. On the outer sides of the two rollers, a support plate is sleeved.

[0009] Through the above technical solution, by setting the base and the support plate, the motor and the roller can be supported respectively, so that the operation of the first motor and the rotation of the rotating shaft can be more stable and firm, thereby achieving the purpose of increasing the service life.

[0010] Further, the two bases and the two support plates are respectively fixedly connected to both sides of the lower belt conveyor. At the connection between the two support plates and the two rollers, they are movably connected through bearings.

[0011] Further, the auxiliary structure includes two travel switch assemblies and two displacement sensor assemblies. The two travel switch assemblies are respectively installed on both sides of the lower belt conveyor. The two displacement sensor assemblies are respectively installed on both sides of the two lower belt conveyors and the two upper belt conveyors. The two travel switch assemblies and the two displacement sensor assemblies are respectively located between the two worm and worm gear lifters.

[0012] Through the above technical solution, by setting the displacement sensor, the purpose of measuring the distance between the upper belt conveyor and the lower belt conveyor in real time can be achieved.

[0013] Further, on both sides of the lower belt conveyor, two guide shaft fixing clips are installed. Inside the four guide shaft fixing clips, a guide shaft is provided. On the outer sides of the four guide shafts, a linear bearing fixing seat is provided. The four linear bearing fixing seats are respectively installed on both sides of the two upper belt conveyors. On the outer sides of the four linear bearing fixing seats, a dead stop is installed.

[0014] Through the above technical solution, by setting four guiding shafts, the lifting movement of the upper belt conveyor can be limited, thereby making the stability of the upper belt conveyor during lifting movement better.

[0015] Furthermore, a load-bearing seat is fixedly connected to the bottom of the support frame. An inner cavity is provided in the bottom of the load-bearing seat, and a bottom plate is fixedly connected to the rear side of the load-bearing seat.

[0016] Through the above technical solution, by setting the bottom plate, the motor two can be supported, thereby making the motor two more stable during operation.

[0017] Furthermore, a motor two is fixedly connected to the top of the bottom plate. A double-headed worm one is fixedly connected to the output shaft of the motor two. A double-headed worm two is provided on one side of the double-headed worm one. The front ends of the double-headed worm one and the double-headed worm two both extend to the inside of the front side of the load-bearing seat.

[0018] Furthermore, the connections between the double-headed worm one and the double-headed worm two and the load-bearing seat are both movably connected through bearings. A pulley one and a pulley two are respectively fixedly sleeved on the outer sides of the double-headed worm one and the double-headed worm two. A belt is sleeved on the outer sides of the pulley one and the pulley two. The pulley one and the pulley two are driven and connected by the belt. The belt one, the belt two, and the belt are all located at the rear side of the load-bearing seat.

[0019] Through the above technical solution, through the mutual cooperation between the belt one, the belt two, and the belt, the double-headed worm one and the double-headed worm two can be rotated synchronously.

[0020] Furthermore, two worm wheels are meshed with the inner sides of the double-headed worm one and the double-headed worm two respectively. The four worm wheels are evenly distributed. Threaded sleeves are fixedly embedded in the four worm wheels. The tops of the four threaded sleeves are all rotatably connected to the top of the load-bearing seat.

[0021] Furthermore, threaded rods are respectively threadedly inserted into the inner sides of the bottoms of the four threaded sleeves. Two cross plates are sleeved on the outer sides of the four threaded rods. Universal wheels are fixedly connected to the bottom ends of the four threaded rods. The two cross plates and the four universal wheels are all located inside the inner cavity.

[0022] Through the above technical solution, by setting two cross plates, the four threaded rods can be limited, thereby enabling the four threaded rods to drive the four universal wheels to move up and down, so as to facilitate the subsequent movement of the mechanism.

[0023] In summary, the present application includes the following beneficial technical effects:

[0024] For this utility model, a regulating mechanism is designed. By the cooperation among multiple structures such as rollers, sprocket one, sprocket two, chains, connecting rods, worm and worm gear lifters, and lifter screw mounting brackets, it solves the problems that the existing hot melt machines have relatively simple structures and functions. The distance between most upper and lower belt lines cannot be quickly adjusted according to the usage regulations of process requirements, resulting in relatively low overall flexibility and poor applicability. Therefore, it will not only reduce practicability and increase the manufacturing cost of products, but also affect the stability of product output.

[0025] For this utility model, the function of synchronously lifting and moving adjustment of four universal wheels is completed through an auxiliary structure, making the movement of the entire device more convenient and fast. To a certain extent, it shortens the operation time and also reduces the labor of the staff. Brief Description of the Drawings

[0026] Figure 1 is the overall structural schematic diagram of this application;

[0027] Figure 2 is the partial sectional perspective view of this application;

[0028] Figure 3 is the partial perspective view of this application;

[0029] Figure 4 is of this application Figure 1 enlarged view of the structure at A in;

[0030] Figure 5 is of this application Figure 3 enlarged view of the structure at B in.

[0031] Explanation of the reference numerals in the drawings:

[0032] 1. Support frame; 2. Upper belt conveyor; 3. Lower belt conveyor; 4. Motor one; 5. Roller; 6. Sprocket one; 7. Sprocket two; 8. Chain; 9. Connecting rod; 10. Worm and worm gear lifter; 11. Lifter screw mounting bracket; 12. Base; 13. Support plate; 14. Travel switch assembly; 15. Displacement sensor assembly; 16. Guide shaft fixing clamp; 17. Guide shaft; 18. Linear bearing fixing seat; 19. Dead stop; 20. Load-bearing seat; 21. Bottom plate; 22. Motor two; 23. Double-headed worm one; 24. Double-headed worm two; 25. Pulley one; 26. Pulley two; 27. Belt; 28. Worm gear; 29. Threaded sleeve; 30. Threaded rod; 31. Cross plate; 32. Universal wheel. Detailed Description of the Preferred Embodiment

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application; obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0034] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "top / bottom end", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0035] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "provided with", "sheathed / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations. Embodiment

[0036] The embodiment of the present application discloses an automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine. Please refer to Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5 , which includes a support frame 1, and an adjustment mechanism is provided outside the support frame 1 and extends into the support frame 1;

[0037] The adjusting mechanism includes an upper belt conveyor 2 and a lower belt conveyor 3. The upper belt conveyor 2 is located at the top of the lower belt conveyor 3. On both sides of the lower belt conveyor 3, there are fixedly connected with a first motor 4. The two first motors 4 are symmetrically arranged before and after with the midline of the lower belt conveyor 3 as the axis. The output shafts of the two first motors 4 are fixedly connected with rollers 5. On the outer sides of the two rollers 5, there are fixedly sleeved with a first sprocket 6. On the top of the two first sprockets 6, there are provided second sprockets 7. On the outer sides of the two first sprockets 6 and the two second sprockets 7, there are sleeved with chains 8. The two first sprockets 6 and the two second sprockets 7 are respectively driven and connected through the two chains 8. Inside the two second sprockets 7, there are fixedly embedded with connecting rods 9. On the outer sides of the two connecting rods 9, there are installed four worm and worm gear lifters 10. The four worm and worm gear lifters 10 are respectively located on one side of the two second sprockets 7. On the outer sides of the tops of the four worm and worm gear lifters 10, there are installed lifter screw mounting brackets 11. The four lifter screw mounting brackets 11 are respectively fixedly connected to both sides of the upper belt conveyor 2;

[0038] Please refer to Figure 1 and Figure 5 , the four worm and worm gear lifters 10 are respectively installed on both sides of the lower belt conveyor 3. On the bottoms of the two first motors 4, there are installed bases 12. On the outer sides of the two rollers 5, there is sleeved with a support plate 13. The two bases 12 and the two support plates 13 are respectively fixedly connected to both sides of the lower belt conveyor 3. The connections between the two support plates 13 and the two rollers 5 are respectively movably connected through bearings. By setting the bases 12 and the support plates 13, the motors and the rollers 5 can be respectively supported, so that the operation of the first motor 4 and the rotation of the rotating shaft can be more stable and firm, thereby achieving the purpose of increasing the service life;

[0039] Please refer to Figure 1 , on the outer sides of the four lifter screw mounting brackets 11, there is an auxiliary structure. The auxiliary structure includes two travel switch assemblies 14 and two displacement sensor assemblies 15. The two travel switch assemblies 14 are respectively installed on both sides of the lower belt conveyor 3. The two displacement sensor assemblies 15 are respectively installed on both sides of the two lower belt conveyors 3 and the two upper belt conveyors 2. The two travel switch assemblies 14 and the two displacement sensor assemblies 15 are respectively located between the two worm and worm gear lifters 10. By setting the displacement sensors, the purpose of measuring the distance between the upper belt conveyor 2 and the lower belt conveyor 3 in real time can be achieved;

[0040] Please refer to Figure 1 and Figure 2, two guiding shaft fixing clips 16 are installed on both sides of the lower belt conveyor 3. Four guiding shafts 17 are provided inside the four guiding shaft fixing clips 16. Linear bearing fixing seats 18 are provided outside the four guiding shafts 17. The four linear bearing fixing seats 18 are respectively installed on both sides of the two upper belt conveyors 2. Dead stops 19 are installed outside the four linear bearing fixing seats 18. A load-bearing seat 20 is fixedly connected to the bottom of the support frame 1. An inner cavity is opened at the bottom of the load-bearing seat 20. A bottom plate 21 is fixedly connected to the rear side of the load-bearing seat 20. By providing four guiding shafts 17, the lifting movement of the upper belt conveyor 2 can be limited, so that the stability of the upper belt conveyor 2 during lifting movement can be better. At the same time, by providing the bottom plate 21, the motor two 22 can be supported, so that the motor two 22 can be more firmly fixed during operation;

[0041] Please refer to Figure 2 , Figure 3 and Figure 5 , a motor two 22 is fixedly connected to the top of the bottom plate 21. The output shaft of the motor two 22 is fixedly connected to a double-headed worm one 23. A double-headed worm two 24 is provided on one side of the double-headed worm one 23. The front ends of the double-headed worm one 23 and the double-headed worm two 24 both extend to the front side inside the load-bearing seat 20. The connections between the double-headed worm one 23 and the double-headed worm two 24 and the load-bearing seat 20 are both movably connected through bearings. A pulley one 25 and a pulley two 26 are respectively fixedly sleeved outside the double-headed worm one 23 and the double-headed worm two 24. A belt 27 is sleeved outside both the pulley one 25 and the pulley two 26. The pulley one 25 and the pulley two 26 are drivingly connected through the belt 27. The belt 27 one, the belt 27 two and the belt 27 are all located at the rear side of the load-bearing seat 20. Through the mutual cooperation among the belt 27 one, the belt 27 two and the belt 27, the double-headed worm one 23 and the double-headed worm two can rotate synchronously;

[0042] Please refer to Figure 2 , two worm wheels 28 are meshed inside both the double-headed worm one 23 and the double-headed worm two 24. The four worm wheels 28 are evenly distributed. Threaded sleeves 29 are fixedly embedded inside the four worm wheels 28. The tops of the four threaded sleeves 29 are all rotatably connected to the top of the load-bearing seat 20. Threaded rods 30 are threadedly inserted into the inner sides of the bottoms of the four threaded sleeves 29. Two cross plates 31 are sleeved outside the four threaded rods 30. Universal wheels 32 are fixedly connected to the bottoms of the four threaded rods 30. The two cross plates 31 and the four universal wheels 32 are all located inside the inner cavity. By providing the two cross plates 31, the four threaded rods 30 can be limited, so that the four threaded rods 30 can drive the four universal wheels 32 to move up and down, so as to facilitate the subsequent movement of this mechanism.

[0043] The implementation principle of this embodiment is as follows: When in use and it is necessary to increase the distance between the upper belt conveyor 2 and the lower belt conveyor 3, the power supply can be started, so that the output shafts of the two motors 4 drive the two rollers 5 to rotate respectively. The two rollers 5 drive the two sprockets 6 to rotate respectively. The two sprockets 6 cooperate with the two sprockets 7 and the two chains 8, so that the two connecting rods 9 rotate. Subsequently, the two connecting rods 9 cooperate with the four worm and worm gear lifters 10, so that the input shafts of the four worm and worm gear lifters 10 rotate. Since there are four lifter body mounting brackets installed between the four worm and worm gear lifters 10 and the lower belt conveyor 3, the stability of the four worm and worm gear lifters 10 can be enhanced. At this time, the four worm and worm gear lifters 10 are in synchronous operation. At this time, the upper belt conveyor 2 will be driven to move upward along the vertical direction of the guide shaft 17 by the four lifter screw mounting brackets 11;

[0044] Because two displacement sensor components 15 are installed, the purpose of real-time measuring the distance between the upper belt conveyor 2 and the lower belt conveyor 3 can be achieved. At the same time, because there is also a travel switch component 14 and a dead stop additionally, when it reaches the maximum value and cannot rise anymore, the travel switch paddle will be sensed first. On the contrary, if it is necessary to reduce the distance between the two belt lines 27, just reverse the motor 4 to achieve it. Through the above structure, the problems are solved that because the existing hot melt machine structure is relatively single and the function is relatively single, the distance between most upper and lower belt lines 27 cannot be quickly adjusted according to the usage regulations of the process requirements, the overall flexibility is relatively low, the applicability is relatively poor, so it will not only cause the reduction of practicability and increase the manufacturing cost of the product, but also affect the stability of product output;

[0045] In the later stage, the staff can also turn on the power supply to make the motor 22 drive the double-headed worm 23 to rotate. The double-headed worm 23 cooperates with the pulley 25, the pulley 26 and the belt 27, so that the double-headed worm 24 rotates. Subsequently, the double-headed worm 23 and the double-headed worm 24 cooperate with the four worm wheels 28, so that the four threaded sleeves 29 rotate. Since two cross plates 31 are fixedly sleeved on the outer sides of the four threaded rods 30, the two cross plates 31 can limit the four threaded rods 30, so the four threaded rods 30 can drive the four universal wheels 32 to move downward. When the four universal wheels 32 all move downward to the bottom of the bearing seat 20, the function of convenient movement can be realized. When it moves to the designated position, just reverse the motor 22 again.

[0046] The above are all the preferred embodiments of this application. It does not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of this application should be covered within the protection scope of this application.

Claims

1. An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine, including a support frame (1), characterized in that: An adjustment mechanism is provided on the outer side of the support frame (1), and the adjustment mechanism extends into the support frame (1); The adjustment mechanism includes an upper belt conveyor (2) and a lower belt conveyor (3). The upper belt conveyor (2) is located on top of the lower belt conveyor (3). Both sides of the lower belt conveyor (3) are fixedly connected with a first motor (4). The two first motors (4) are symmetrically arranged front and back with the midline of the lower belt conveyor (3) as the axis. The output shafts of the two first motors (4) are fixedly connected with rollers (5). Both outer sides of the two rollers (5) are fixedly sleeved with a first sprocket (6). A second sprocket (7) is provided on top of each of the two first sprockets (6). Chains (8) are sleeved on the outer sides of the two first sprockets (6) and the two second sprockets (7). The two first sprockets (6) and the two second sprockets (7) are respectively driven and connected by the two chains (8). A connecting rod (9) is fixedly embedded inside each of the two second sprockets (7). Two worm gear and worm lifters (10) are installed on the outer sides of the two connecting rods (9). The four worm gear and worm lifters (10) are respectively located on one side of the two second sprockets (7). An elevator screw mounting bracket (11) is installed on the outer side of the top of each of the four worm gear and worm lifters (10). The four elevator screw mounting brackets (11) are respectively fixedly connected to both sides of the upper belt conveyor (2). An auxiliary structure is provided on the outer sides of the four elevator screw mounting brackets (11).

2. The automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 1, characterized in that: The four worm gear and worm lifters (10) are respectively installed on both sides of the lower belt conveyor (3). A base (12) is installed at the bottom of each of the two first motors (4). A support plate (13) is sleeved on the outer sides of the two rollers (5).

3. An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 2, characterized in that: The two bases (12) and the two support plates (13) are respectively fixedly connected to both sides of the lower belt conveyor (3). The connections between the two support plates (13) and the two rollers (5) are respectively movably connected through bearings.

4. An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 1, characterized in that: The auxiliary structure includes two travel switch assemblies (14) and two displacement sensor assemblies (15). The two travel switch assemblies (14) are respectively installed on both sides of the lower belt conveyor (3). The two displacement sensor assemblies (15) are respectively installed on both sides of the two lower belt conveyors (3) and the two upper belt conveyors (2). The two travel switch assemblies (14) and the two displacement sensor assemblies (15) are respectively located between the two worm gear and worm lifters (10).

5. An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 1, characterized in that: Two guide shaft fixing clips (16) are installed on both sides of the lower belt conveyor (3). Guide shafts (17) are provided inside the four guide shaft fixing clips (16). Linear bearing fixing seats (18) are provided on the outer sides of the four guide shafts (17). The four linear bearing fixing seats (18) are respectively installed on both sides of the two upper belt conveyors (2). Dead stops (19) are installed on the outer sides of the four linear bearing fixing seats (18).

6. The automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 1, characterized in that: A load-bearing seat (20) is fixedly connected to the bottom of the support frame (1). An inner cavity is opened at the bottom of the load-bearing seat (20). A bottom plate (21) is fixedly connected to the rear side of the load-bearing seat (20).

7. An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 6, characterized in that: A second motor (22) is fixedly connected to the top of the bottom plate (21). A double-headed worm one (23) is fixedly connected to the output shaft of the second motor (22). A double-headed worm two (24) is provided on one side of the double-headed worm one (23). The front ends of the double-headed worm one (23) and the double-headed worm two (24) both extend to the inside of the front side of the load-bearing seat (20).

8. An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 7, characterized in that: The connections between the double-headed worm one (23) and the double-headed worm two (24) and the load-bearing seat (20) are both movably connected through bearings. A pulley one (25) and a pulley two (26) are respectively fixedly sleeved on the outer sides of the double-headed worm one (23) and the double-headed worm two (24). Belts (27) are sleeved on the outer sides of the pulley one (25) and the pulley two (26). The pulley one (25) and the pulley two (26) are drivingly connected through the belt (27). The belt one (27), the belt two (27) and the belt (27) are all located at the rear side of the load-bearing seat (20).

9. An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 7, characterized in that: Two worm wheels (28) are meshed on the inner sides of both the double-headed worm one (23) and the double-headed worm two (24). The four worm wheels (28) are evenly distributed. Threaded sleeves (29) are fixedly embedded in the four worm wheels (28). The tops of the four threaded sleeves (29) are all rotatably connected to the top of the load-bearing seat (20).

10. An automatic distance adjustment mechanism for the upper and lower belt conveyors of a cowhide hot melt machine according to claim 9, characterized in that: Threaded rods (30) are threadedly inserted into the inner sides of the bottoms of the four threaded sleeves (29). Two cross plates (31) are sleeved on the outer sides of the four threaded rods (30). Universal wheels (32) are fixedly connected to the bottoms of the four threaded rods (30). The two cross plates (31) and the four universal wheels (32) are all located inside the inner cavity.

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