Die penetrating device of longitudinal stretching machine

Abstract

The utility model discloses a mold penetrating device of a longitudinal stretching machine, which comprises a first belt and a second belt which are sequentially arranged along the vertical direction, the bottom of the first belt is adjacently connected with the top of the second belt along the vertical direction, and the first belt and the second belt are synchronous conveying belts in the same direction; a thick sheet inlet and a thick sheet outlet are formed in the two ends of the first belt and the two ends of the second belt respectively in the transmission direction of the first belt and the second belt, the polymer thick sheet abuts against the first belt and the second belt from the thick sheet inlet, and the first belt and the second belt drive the polymer thick sheet to sequentially pass through the rollers and then stretch out of the thick sheet outlet. According to the membrane penetrating device, membrane penetrating work can be directly carried out on a polymer thick sheet, the whole process is more convenient and faster, a cotton rope cleaning process is omitted, the membrane penetrating device is cleaner and tidier, cotton ropes do not need to be cleaned, the number of times for workers to make contact with equipment is reduced, safety is improved, and reliability is improved for follow-up operation of the equipment.

Description

Technical Field

[0001] This utility model relates to the field of film forming equipment, and in particular to a die-threading device for a longitudinal stretching machine. Background Technology

[0002] The demand for film plastic products is increasing in today's society, and they are involved in our daily lives. Among them, polypropylene (PP) and polyethylene terephthalate (PET) products are particularly prominent. The equipment for producing polypropylene products includes the following important single machines: raw material system, extrusion system, sheet forming system, longitudinal stretching system, transverse stretching system, traction system, and winding system.

[0003] As is well known, polymer sheets often require stretching and orientation treatment to fully utilize their properties. Longitudinal stretching involves elongating the extruded polymer sheets longitudinally using metal rollers. Typically, the polymer sheet is tied to a chain with a rope, and a chain motor drives the sheet along the rollers until it reaches the outlet of the longitudinal stretching system. The chain motor is then stopped, the rope is cut, and the sheet is removed. This process is cumbersome and inconvenient. Furthermore, the rope must be cut manually at the outlet, posing a safety hazard to workers. The cut rope often becomes tangled in the chain and is difficult to clean, requiring regular cleaning during each machine shutdown for maintenance; otherwise, it can affect subsequent polymer sheet stretching over time. Utility Model Content

[0004] The purpose of this invention is to solve the problem that existing polymer sheet stretching processes are cumbersome, require rope traction, and are inherently dangerous. This invention provides a die-threading device for a longitudinal stretching machine, which can directly thread polymer sheets through the film. The entire process is more convenient and faster, eliminates the need for rope cleaning, and results in a cleaner and more efficient stretching process. Furthermore, the elimination of rope cleaning reduces the number of times workers need to handle the equipment, increases safety, and improves the reliability of subsequent equipment operation.

[0005] To solve the above-mentioned technical problems, the present invention discloses a die-cutting device for a longitudinal stretching machine, used for longitudinally stretching polymer sheets, comprising:

[0006] A first belt and a second belt are arranged in sequence along the vertical direction. The first belt is located above the second belt, and the bottom of the first belt and the top of the second belt are adjacent to each other in the vertical direction. The first belt and the second belt are synchronous conveyor belts in the same direction.

[0007] Along the transmission direction of the first belt and the second belt, the first belt and the second belt are respectively provided with a thick sheet inlet and a thick sheet outlet at their ends. The polymer thick sheet abuts against the first belt and the second belt at the thick sheet inlet. The first belt and the second belt drive the polymer thick sheet to pass through multiple rollers in sequence and then extend out from the thick sheet outlet.

[0008] Using the above technical solution, polymer sheets can be directly threaded through the film, making the whole process more convenient and faster. There is no need to clean the ropes, and the entire stretching process is cleaner and tidier. At the same time, the elimination of rope cleaning reduces the number of times workers come into contact with the equipment, increasing the safety of the work process and the reliability of equipment operation.

[0009] According to another specific embodiment of the present invention, the embodiment of the present invention discloses that both the first belt and the second belt are wedge-shaped belts, and the outer surfaces of both the first belt and the second belt are provided with multiple wedge-shaped grooves, the multiple wedge-shaped grooves making the cross-section of the first belt and the second belt wedge-shaped.

[0010] According to another specific embodiment of the present invention, the embodiment of the present invention also includes a frame, on which a plurality of first guide wheel sets are provided and fixed on the frame according to a preset position. A first belt is sequentially wound around the plurality of first guide wheel sets, and the first belt is supported by the plurality of first guide wheel sets and rotates around the plurality of first guide wheel sets.

[0011] According to another specific embodiment of the present invention, the embodiment of the present invention further includes a plurality of second guide wheel groups, which are fixed on the frame at preset positions. A second belt is sequentially wound around the plurality of second guide wheel groups, and the second belt is supported by the plurality of second guide wheel groups and rotates around the plurality of second guide wheel groups.

[0012] According to another specific embodiment of the present invention, the embodiment of the present invention discloses that it also includes a plurality of tensioning wheel assemblies, which are disposed on the frame. The tensioning wheel assemblies abut against the inner sides of the first belt and the second belt respectively, for tensioning the first belt and the second belt.

[0013] According to another specific embodiment of the present invention, the embodiment of the present invention discloses a tensioning wheel assembly comprising:

[0014] The cylinder is fixedly mounted on the frame. The cylinder includes a cylinder and a piston rod. The cylinder drives the piston rod to make linear reciprocating motion inside the cylinder by air pressure.

[0015] The tension wheel includes a wheel body and a bearing located at the center of the wheel body. A connecting piece is connected to the bearing and is fixedly connected to the piston rod. The tension wheel is moved by the piston rod.

[0016] The tension pulleys abut against the inner sides of the first and second belts, respectively.

[0017] According to another specific embodiment of the present invention, the embodiment of the present invention discloses that it also includes a driving device, which includes a drive motor assembly and a first pulley and a second pulley respectively connected to the drive motor assembly.

[0018] The first pulley abuts against the inner side of the first belt, and the drive motor drives the first pulley to rotate and drives the first belt to rotate around the first guide wheel assembly.

[0019] The second pulley abuts against the inner side of the second belt, and the drive motor drives the second pulley to rotate and causes the second belt to rotate around the second guide wheel assembly.

[0020] According to another specific embodiment of the present invention, the embodiment of the present invention discloses a drive motor assembly comprising:

[0021] The drive motor is rotatably connected to the second pulley.

[0022] The first turbine assembly is rotatably connected to the second pulley, and the drive shaft of the drive motor is rotatably connected to the first turbine assembly to drive the first turbine assembly to rotate.

[0023] The second turbine assembly is rotatably connected to the first pulley, and the first turbine assembly and the second turbine assembly are rotatably connected by a worm gear;

[0024] When the drive motor drives the second pulley to rotate, the drive motor also drives the first turbine group, the second turbine group and the first pulley to rotate synchronously.

[0025] The beneficial effects of this application are as follows: by providing a die-threading device for a longitudinal stretching machine, polymer sheets can be directly threaded through the film, making the whole process more convenient and faster, and eliminating the need for cleaning up the ropes. The entire stretching process is cleaner and tidier, and the elimination of rope cleaning reduces the number of times workers come into contact with the equipment, increases the safety of the work process, and improves the reliability of subsequent equipment operation. Attached Figure Description

[0026] Fig. 1 This diagram shows a structural schematic of the die-threading device of the longitudinal stretching machine according to an embodiment of the present invention;

[0027] Fig. 2 This diagram shows a structural schematic of the tensioning wheel assembly according to an embodiment of the present invention;

[0028] Fig. 3 A schematic diagram of the drive device according to an embodiment of the present invention is shown. Detailed Implementation

[0029] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Although the description of this utility model will be presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. On the contrary, the purpose of describing the utility model in conjunction with the embodiments is to cover other options or modifications that may be derived based on the claims of this utility model. To provide a deep understanding of this utility model, many specific details will be included in the following description. This utility model may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this utility model, some specific details will be omitted in the description. It should be noted that, without conflict, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0030] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] In the description of this embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the utility model.

[0032] The terms “first”, “second”, etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0033] In the description of this embodiment, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0034] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0035] Reference Figs. 1 to 3 This application provides a die-cutting device for a longitudinal stretching machine, used for longitudinally stretching polymer sheets, comprising:

[0036] Along the vertical direction ( Fig. 1 (As shown in the Y direction) A first belt 1 and a second belt 2 are arranged in sequence. The first belt 1 is located above the second belt 2. The bottom of the first belt 1 and the top of the second belt 2 are adjacent to each other in the vertical direction. The first belt 1 and the second belt 2 are synchronous and co-directional conveyor belts.

[0037] Along the transmission direction of the first belt 1 and the second belt 2, the two ends of the first belt 1 and the second belt 2 are respectively provided with a thick sheet inlet 5 and a thick sheet outlet 6. The polymer thick sheet abuts against the first belt 1 and the second belt 2 at the thick sheet inlet 5 respectively. The first belt 1 and the second belt 2 drive the polymer thick sheet to pass through multiple rollers 8 in sequence and then extend out from the thick sheet outlet 6.

[0038] In this embodiment, the first belt 1 and the second belt 2 are arranged in a vertically stacked position, with the first belt 1 located above the second belt 2. The bottom of the first belt 1 and the top of the second belt 2 are adjacent to each other in the vertical direction and are synchronous and co-directional conveyor belts. The two ends of the first belt 1 and the second belt 2 are respectively provided with a thick sheet inlet 5 and a thick sheet outlet 6.

[0039] When the polymer sheet enters from the sheet inlet 5, it will simultaneously come into close contact with the first belt 1 and the second belt 2, ensuring that the polymer sheet can be stably clamped by the first belt 1 and the second belt 2 before entering the stretching stage, and ensuring that the polymer sheet is between the first belt 1 and the second belt 2 without any deviation or slippage.

[0040] As the polymer sheet is driven by the first belt 1 and the second belt 2, it begins to move towards the inner roller 8. Multiple rollers 8 are arranged in a preset order along the driving direction of the first belt 1 and the second belt 2. The rollers 8 contain multiple roller groups with different functions, usually composed of rollers of different diameters and / or different materials.

[0041] When passing through roller 8, roller 8 will rotate synchronously at a preset speed to assist in driving the polymer sheet through the mold. After passing through a series of rollers 8, the polymer sheet reaches the sheet outlet 6 and extends out from there, completing the process of the polymer sheet through the mold.

[0042] Compared to existing methods that involve perforating polymer sheets and binding them to a chain with a rope for stretching, the die-threading device of this longitudinal stretching machine allows the polymer sheets to be directly threaded through the mold via the coordinated transport of the first belt 1 and the second belt 2. This eliminates the need for perforation and enables the polymer sheets to be directly threaded between the rollers 8. The entire process is more convenient and faster, and there is no need to clean up the ropes. The stretching process is cleaner and more efficient. Furthermore, the elimination of rope cleaning reduces the number of times workers need to touch the equipment, increasing safety and improving the reliability of subsequent equipment operation.

[0043] In one applicable embodiment, both the first belt 1 and the second belt 2 are wedge-shaped belts, and the outer surfaces of both the first belt 1 and the second belt 2 are provided with multiple wedge-shaped grooves, which make the cross-sections of the first belt 1 and the second belt 2 wedge-shaped.

[0044] In this embodiment, the first belt 1 and the second belt 2 are key transmission components for driving the polymer sheet. The wedge-shaped belt design enables the first belt 1 and the second belt 2 to better transmit power during transmission, reduce slippage when driving the polymer sheet, and improve transmission efficiency.

[0045] Multiple wedge-shaped grooves are formed on the outer surfaces of both the first belt 1 and the second belt 2. The design of these wedge-shaped grooves can increase the friction between the first belt 1 and the second belt 2.

[0046] In one applicable embodiment, the device further includes a frame on which a plurality of first guide wheel sets 3 are provided and fixed in a preset position. A first belt 1 is sequentially wound around the plurality of first guide wheel sets 3. The first belt 1 is supported by the plurality of first guide wheel sets 3 and rotates around the plurality of first guide wheel sets 3.

[0047] It also includes multiple second guide wheel sets 4, which are fixed on the frame in preset positions. The second belt 2 is sequentially wound around the multiple second guide wheel sets 4, and the second belt 2 is supported by the multiple second guide wheel sets 4 and rotates around the multiple second guide wheel sets 4.

[0048] In this embodiment, the frame serves as the basic support structure for the entire device, possessing sufficient strength and stability. Multiple first guide wheel sets 3 are mounted on the frame, and these sets are fixed to the frame according to pre-designed positions. A first belt 1 is sequentially and tightly wound around the multiple first guide wheel sets 3. During installation, it is necessary to ensure good contact between the first belt 1 and each first guide wheel set 3, so that the first belt 1 can be stably supported by the multiple first guide wheel sets 3 and can rotate smoothly around them.

[0049] Similarly, multiple second guide wheel sets 4 are firmly fixed to the frame at preset specific positions. The second belt 2 is sequentially and orderly wound around the multiple second guide wheel sets 4. During installation, attention should be paid to adjusting the belt tension to ensure that the second belt 2 can be effectively supported by the multiple second guide wheel sets 4 and can rotate smoothly around the multiple second guide wheel sets 4 during equipment operation. Usually, the second guide wheel sets 4 and the first guide wheel sets 3 are symmetrically designed, which can ensure that the second belt 2 and the first belt 1 are synchronously transmitted, while the first belt 1 and the second belt 2 can work together with other related components to ensure the efficient and stable operation of the entire equipment system.

[0050] The first guide wheel assembly 3 includes a first guide wheel and a first bearing. The first bearing is fixedly mounted on the frame, and the first guide wheel is mounted on the first bearing and can rotate on the first bearing. The first guide wheel has a groove that matches the wedge-shaped groove on the first belt 1. When the first belt 1 contacts the first guide wheel, a wedge-shaped clamping force is formed. When the first belt 1 is driven on the first guide wheel, due to the action of the wedge-shaped groove, the first belt 1 will gradually embed into the groove of the first guide wheel, thereby increasing the friction between the first belt 1 and the first guide wheel.

[0051] Similarly, the second guide wheel assembly 4 includes a second guide wheel and a second bearing. The second bearing is fixedly mounted on the frame, and the second guide wheel is mounted on the second bearing and can rotate on the second bearing. The second guide wheel has a groove that matches the wedge groove on the second belt 2 to increase the friction with the second belt 2. Its principle is the same as the clamping principle between the first belt 1 and the first guide wheel, and will not be described again.

[0052] Continue to refer to Fig. 2 In one applicable embodiment, a plurality of tensioning pulley assemblies 7 are further included, disposed on the frame. The tensioning pulley assemblies 7 abut against the inner surfaces of the first belt 1 and the second belt 2, respectively, for tensioning the first belt 1 and the second belt 2. The tensioning pulley assembly 7 includes:

[0053] Cylinder 71 is fixedly mounted on the frame. Cylinder 71 includes cylinder 71 and piston rod. Cylinder 71 drives piston rod to perform linear reciprocating motion in cylinder 71 by air pressure.

[0054] The tension wheel 72 includes a wheel body and a bearing located at the center of the wheel body. A connecting member 73 is connected to the bearing. The connecting member 73 is fixedly connected to the piston rod. The tension wheel 72 is driven to move by the piston rod.

[0055] The tension pulley 72 abuts against the inner sides of the first belt 1 and the second belt 2 respectively.

[0056] In this embodiment, the tensioning pulley group 7 is mounted on the frame and precisely abuts against the inner sides of the first belt 1 and the second belt 2 respectively. Its purpose is to effectively tension the first belt 1 and the second belt 2, ensuring that the belts maintain appropriate tension during operation and avoiding slippage or slack, thereby ensuring the stability and reliability of power transmission.

[0057] The tensioning pulley assembly 7 mainly consists of a cylinder 71 and a tensioning pulley 72. The cylinder 71 is fixedly mounted on the frame and includes a cylinder body and a piston rod. During operation, the cylinder 71 drives the piston rod to perform linear reciprocating motion within the cylinder body. By controlling the air pressure, the extension or retraction length of the piston rod can be adjusted, thereby achieving flexible adjustment of the position of the tensioning pulley 72 and ensuring that the belt maintains appropriate tension throughout operation.

[0058] The tension pulley 72 includes a pulley body and a bearing located at the center of the pulley body. The bearing reduces the frictional resistance when the pulley body rotates, allowing the tension pulley 72 to rotate more smoothly. A connecting member 73 is externally connected to the bearing, and this connecting member 73 is fixedly connected to the piston rod to ensure stable movement of the tension pulley 72 when the piston rod moves. When the piston rod moves linearly under the drive of the cylinder 71, the tension pulley 72 moves synchronously. Since the tension pulley 72 is in close contact with the inner surfaces of the first belt 1 and the second belt 2, its position change directly affects the belt tension. For example, when it is necessary to increase the belt tension, the air pressure of the cylinder 71 is increased to extend the piston rod outward, causing the tension pulley 72 to move outward, thereby applying greater pressure to the belt and tightening it; conversely, when it is necessary to reduce the belt tension, the air pressure is decreased to retract the piston rod, causing the tension pulley 72 to move inward, relaxing the pressure on the belt. In this way, the tensioning pulley group 7 can dynamically adjust the tension of the first belt 1 and the second belt 2 according to the actual operating requirements of the equipment, ensuring the efficient and stable operation of the entire transmission system.

[0059] In one applicable embodiment, a drive device 9 is also included, which includes a drive motor assembly 91 and a first pulley 92 and a second pulley 93 respectively connected to the drive motor assembly 91.

[0060] The first pulley 92 abuts against the inner side of the first belt 1, and the drive motor 91 drives the first pulley 92 to rotate and drives the first belt 1 to rotate around the first guide wheel 3.

[0061] The second pulley 93 abuts against the inner side of the second belt 2, and the drive motor 91 drives the second pulley 93 to rotate and drives the second belt 2 to rotate around the second guide wheel group 4.

[0062] In this embodiment, the drive device 9 is used to provide transmission power to the first belt 1 and the second belt 2. The drive device 9 mainly consists of a drive motor assembly 91 and a first pulley 92 and a second pulley 93 respectively connected to the drive motor assembly 91.

[0063] The first pulley 92 is in close contact with the inner side of the first belt 1 to ensure sufficient friction and prevent slippage during transmission.

[0064] The second pulley 93 also maintains close contact with the inner side of the second belt 2, and its connection with the drive motor assembly 91 is the same as that of the first pulley 92, in order to ensure efficient power transmission. Driven by the motor, the second pulley 93 rotates and drives the second belt 2 to rotate around the second guide pulley assembly 4, working synchronously with the transmission line of the first belt 1.

[0065] By using the same drive motor 91 to drive the first pulley 92 and the second pulley 93, the first belt 1 and the second belt 2 can be synchronously transmitted.

[0066] Continue to refer to Fig. 3 In one applicable embodiment, the drive motor assembly 91 includes:

[0067] The drive motor 911 is rotatably connected to the second pulley 93;

[0068] The first turbine assembly 912 is rotatably connected to the second pulley 93, and the drive shaft of the drive motor 911 is rotatably connected to the first turbine assembly 912 to drive the first turbine assembly 912 to rotate.

[0069] The second turbine assembly 914 is rotatably connected to the first pulley 92, and the first turbine assembly 912 and the second turbine assembly 914 are rotatably connected by a worm gear 913.

[0070] When the drive motor 911 drives the second pulley 93 to rotate, the drive motor 911 also drives the first turbine group 912, the second turbine group 914 and the first pulley 92 to rotate synchronously.

[0071] In this embodiment, the first pulley 92 and the second pulley 93 are driven by the first turbine group 912 and the second turbine group 914 to achieve synchronous rotation. The drive motor 911 is rotatably connected to the second pulley 93 through its output shaft. The first turbine group 912 is also rotatably connected to the drive motor 911. The second pulley 93 and the first turbine group 912 rotate synchronously under the drive of the drive motor 911.

[0072] The first turbine assembly 912 and the second turbine assembly 914 are vertically aligned and connected vertically. They are connected by a worm gear 913. The turbine of the first turbine assembly 912 and the worm gear 913 change the output direction of the drive motor 911, achieving a 90-degree steering transmission to transfer power to the second turbine assembly 914. The second turbine assembly 914 is rotatably connected to the first pulley 92, and they rotate synchronously. This allows the first pulley 92 and the second pulley 93 to rotate synchronously with only one drive motor 911.

[0073] Although the present invention has been illustrated and described with reference to certain preferred embodiments, those skilled in the art should understand that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the present invention to these descriptions. Those skilled in the art can make various changes in form and detail, including some simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A die-cutting device for a longitudinal stretching machine, used for longitudinally stretching polymer sheets, characterized in that, include: A first belt and a second belt are arranged sequentially along the vertical direction. The first belt is located above the second belt, and the bottom of the first belt and the top of the second belt are adjacent to each other along the vertical direction. The first belt and the second belt are synchronous conveyor belts in the same direction. Along the transmission direction of the first belt and the second belt, the first belt and the second belt are respectively provided with a thick sheet inlet and a thick sheet outlet at both ends. The polymer thick sheet abuts against the first belt and the second belt at the thick sheet inlet. The first belt and the second belt drive the polymer thick sheet to pass through multiple rollers in sequence and then extend out from the thick sheet outlet.

2. The die-threading device of the longitudinal stretching machine as described in claim 1, characterized in that, Both the first belt and the second belt are wedge-shaped belts, and multiple wedge-shaped grooves are formed on the outer surface of both belts, making the cross-section of the first belt and the second belt wedge-shaped.

3. The die-threading device of the longitudinal stretching machine as described in claim 1, characterized in that, It also includes a frame, on which a plurality of first guide wheel sets are provided and fixed in a preset position on the frame. The first belt is sequentially wound around the plurality of first guide wheel sets. The first belt is supported by the plurality of first guide wheel sets and rotates around the plurality of first guide wheel sets.

4. The die-cutting device of the longitudinal stretching machine as described in claim 3, characterized in that, It also includes multiple second guide wheel sets, which are fixed on the frame at preset positions. The second belt is sequentially wound around the multiple second guide wheel sets, and the second belt is supported by the multiple second guide wheel sets and rotates around the multiple second guide wheel sets.

5. The die-threading device of the longitudinal stretching machine as described in claim 3, characterized in that, It also includes multiple tensioning wheel sets, which are disposed on the frame. The tensioning wheel sets abut against the inner sides of the first belt and the second belt respectively, for tensioning the first belt and the second belt.

6. The die-cutting device of the longitudinal stretching machine as described in claim 5, characterized in that, The tensioning wheel assembly includes: A cylinder is fixedly mounted on the frame. The cylinder includes a cylinder and a piston rod. The cylinder drives the piston rod to perform linear reciprocating motion within the cylinder by air pressure. The tension wheel includes a wheel body and a bearing disposed at the center of the wheel body. A connecting member is externally connected to the bearing and the connecting member is fixedly connected to the piston rod. The tension wheel is driven to move by the piston rod. The tensioning pulley abuts against the inner sides of the first belt and the second belt, respectively.

7. The die-cutting device of the longitudinal stretching machine as described in claim 4, characterized in that, It also includes a drive unit, which includes a drive motor assembly and a first belt and a second pulley respectively connected to the drive motor assembly; The first pulley abuts against the inner side of the first belt, and the drive motor drives the first pulley to rotate and causes the first belt to rotate around the first guide wheel assembly; The second pulley abuts against the inner side of the second belt, and the drive motor drives the second pulley to rotate and causes the second belt to rotate around the second guide wheel assembly.

Images