Flanging mechanism matched with bag sewing machine

Abstract

The utility model discloses a flanging mechanism matched with a bag sewing machine for use. The flanging mechanism structurally comprises a connecting support, a movable support and a main and auxiliary assembly frame. The main assembling frame is fixed in the connecting support, the movable support is installed on the connecting support in a sliding mode, and supporting springs are arranged to enhance adaptability of different packaging bags. An auxiliary assembly frame is installed on the movable support and arranged opposite to the main assembly frame. The mechanism is further provided with a first flanging wheel, a second flanging wheel, a first flanging wheel and a second flanging wheel, wherein the first flanging wheel and the second flanging wheel are assembled on the main assembling frame and the auxiliary assembling frame respectively. Transmission rollers are installed on the main assembly frame and the auxiliary assembly frame so as to keep opposite arrangement. By means of the design, completeness and smoothness in the flanging process are guaranteed, and the flanging device can adapt to packaging bags of different materials and thicknesses. And the stable operation action has obvious significance for improving the automation level and standard of the packaging industry.

Description

Technical Field

[0001] This utility model relates to the technical field of supporting mechanisms for bag sewing machines, specifically a flanging mechanism for a bag sewing machine. Background Technology

[0002] In the modern packaging industry, bag sewing machines, as one of the key pieces of equipment, undertake the important task of sealing packaging bags to ensure the integrity and safety of products. Bag sewing machines typically need to be used in conjunction with a folding mechanism to fold the edges of the packaging bag before sewing. This not only improves the overall strength of the packaging but also enhances its sealing and aesthetics. However, existing bag sewing machines generally suffer from several technical problems related to the folding mechanism.

[0003] Firstly, many existing bag-sewing machines lack efficient and reliable folding mechanisms. During the packaging process, the packaging machine often only handles material measurement and filling, while the sewing machine seals the bag after it has been delivered. In this process, folding the edges of the bag often requires manual operation or the use of inefficient folding equipment, which not only reduces production efficiency but also fails to guarantee the quality and consistency of the folding.

[0004] Secondly, even sewing machines equipped with folding mechanisms have numerous problems. Traditional folding mechanisms often struggle to adapt to packaging bags of varying thicknesses and materials, especially when handling thin or soft materials. Issues such as incomplete, uneven, or rough folding frequently occur. These problems directly impact the quality of the sewn packaging and may even lead to damage during subsequent transportation and storage, affecting product protection and its market image.

[0005] Furthermore, existing flanging mechanisms are often complex in design, containing multiple moving parts. This not only increases the failure rate of the machinery but also raises maintenance costs and technical requirements. For example, some flanging mechanisms require fine-tuning the positions of multiple components to adapt to packaging bags of different sizes. Such adjustments are not only time-consuming but also require professional operators, limiting the flexible deployment of bag sewing machines on different production lines.

[0006] Finally, inaccurate positioning of the packaging bags during transport is also a significant factor contributing to the flanging problem. During the process of conveying the packaging bags from the packaging machine to the sewing machine, due to inaccurate positioning of the conveying mechanism or deformation of the packaging bags themselves, the edges of the packaging bags often fail to align precisely with the flanging mechanism, resulting in uneven flanging or incorrect sewing positions. This not only affects the appearance of the product but may also impair the sealing performance of the seal. Utility Model Content

[0007] In view of the above-mentioned shortcomings in the existing technology, the purpose of this utility model is to provide a flange-flipping mechanism for a bag sewing machine, which can ensure the integrity and flatness of the flange, has the advantages of strong adaptability to packaging bags of different materials and thicknesses, and has high operational stability. It has great practical significance for improving the automation level and packaging standards of the modern packaging industry.

[0008] The technical solution adopted by this utility model to achieve the above-mentioned objective is: a flanging mechanism for a bag sewing machine, including a connecting bracket, a movable bracket, a main assembly bracket, and a secondary assembly bracket. The main assembly bracket is fixedly installed in the connecting bracket. The movable bracket includes two sets that are slidably installed in the connecting bracket, and a support spring is installed between the movable bracket and the connecting bracket. A secondary assembly bracket is fixedly installed on each set of movable brackets. The main assembly bracket and the secondary assembly bracket are arranged in a relative manner.

[0009] It also includes a first folding wheel, a second folding wheel, a first flanging wheel, a second flanging wheel, and a transfer roller. The first folding wheel and the second folding wheel are arranged in a relatively opposite manner and are rotatably mounted on the main assembly frame and one of the sub-assembly frames, respectively. The first flanging wheel and the second flanging wheel are rotatably mounted on the main assembly frame and are arranged sequentially on the downstream side of the first folding wheel. The transfer rollers are rotatably mounted on both the main assembly frame and the sub-assembly frame, and the transfer rollers mounted on the main assembly frame and the sub-assembly frame are arranged in a relatively opposite manner.

[0010] In some implementations, to ensure that the movable bracket can be stably assembled on the connecting bracket in a relatively sliding manner, and to ensure that the support spring can stably drive the movable bracket to move towards the main assembly frame, the following technical solutions are provided.

[0011] The bottom of the connecting bracket is fixedly connected to a bearing base plate. Guide grooves are provided on the top of the connecting bracket and the bearing base plate. Guide seats are fixedly connected to the upper and lower sides of the movable bracket. The guide seats and guide grooves are in a sliding combination. A guide post is fixedly connected to the outer side of the movable bracket and is in a sliding insertion with the side wall of the connecting bracket. The support spring is wound around the periphery of the guide post, and the two ends of the support spring are respectively in contact with the movable bracket and the connecting bracket.

[0012] In some implementations, the following technical solutions are provided to ensure that each folding wheel and flanging wheel can effectively fold and flang the opening of the passing packaging bag.

[0013] The first folding wheel has an annular protrusion on its top outer edge, and the second folding wheel has an annular recess on its top outer edge that matches the annular protrusion. Both the first and second folding wheels have folding annular grooves on their outer edges.

[0014] In some implementations, to ensure that the No. 1 folding wheel and the transfer roller mounted on the main assembly frame operate synchronously, to ensure that the No. 2 folding wheel and the transfer roller mounted on one set of sub-assembly frames operate synchronously, and to ensure that the transfer roller mounted on another set of sub-assembly frames operates synchronously, the following technical solutions are provided.

[0015] Synchronous pulleys are fixed to the same end of the first folding wheel, the second folding wheel, and each set of transmission rollers. The synchronous pulleys on the main assembly frame are powered by synchronous belts, and the synchronous pulleys on the two sets of auxiliary assembly frames are powered by two sets of synchronous belts respectively.

[0016] In some implementations, to ensure that the transfer rollers and the first folding roller on the main assembly frame and the second folding roller on the auxiliary assembly frame maintain opposite and equal speed operation, the following technical solutions are provided.

[0017] It also includes a drive motor, a splined shaft, a first drive bevel gear, a second drive bevel gear, and a transmission bevel gear. The drive motor is fixedly mounted on the connecting bracket. The splined shaft includes two sets arranged side by side. The two sets of splined shafts are rotatably mounted on the connecting bracket and the main assembly frame and pass through the movable bracket. One set of splined shafts is powered by the drive motor. A first drive bevel gear is fixedly connected to each of the two sets of splined shafts. A second drive bevel gear is rotatably mounted on each of the two sets of auxiliary assembly frames. The two sets of second drive bevel gears are slidably inserted into the two sets of sliding shafts respectively. The transmission bevel gear is mounted on some of the transmission rollers. The transmission bevel gear is meshed with the first drive bevel gear or the second drive bevel gear at the corresponding position.

[0018] The beneficial effects of this utility model are:

[0019] The main assembly frame, sub-assembly frame, and the conveyor rollers mounted on them ensure stable transfer of packaging bags between them. The assembled folding and turning rollers efficiently and reliably turn the bag openings, ensuring the integrity and flatness of the turned edges. This is crucial for improving the automation level and packaging quality of the sewing machine. The sub-assembly frame is mounted on two independent movable supports, with guide structures and support springs restricting the horizontal movement of these supports. This effectively clamps and stably transfers the packaging bags before and after turning, offering strong adaptability to packaging bags of different materials and thicknesses. Furthermore, the conveyor rollers and folding rollers are driven by a single motor and matching transmission components, ensuring high operational stability and accurate positioning, thus guaranteeing the stability of the turning mechanism. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of this utility model;

[0021] Figure 2 This is a structural schematic diagram from another perspective of the present invention;

[0022] Figure 3 This is a schematic diagram of the connecting bracket structure;

[0023] Figure 4 This is a schematic diagram of the structure of two sets of movable supports;

[0024] Figure 5 A structural schematic diagram of the main assembly frame and the components mounted on it;

[0025] Figure 6 This is a structural diagram of one of the sub-assembly racks and the components mounted on it.

[0026] Figure 7 This is a structural diagram of another set of sub-assemblies and the components mounted on them;

[0027] Figure 8 A structural diagram showing the main assembly frame, two sets of auxiliary assembly frames, and the components mounted on them.

[0028] Figure 9 A schematic diagram of the structure when two sets of folding wheels are combined;

[0029] Figure 10 This is a schematic diagram of the structure of the two sets of flanging wheels in the cut state.

[0030] In the diagram: 1 connecting bracket, 11 bearing base plate, 12 guide groove, 2 movable bracket, 21 support spring, 22 guide seat, 23 guide column, 31 main assembly frame, 32 auxiliary assembly frame, 33 bolt assembly, 41 first folding wheel, 411 annular protrusion, 42 second folding wheel, 421 annular recess, 51 first flanging wheel, 52 second flanging wheel, 53 flanging ring groove, 6 transmission roller, 71 synchronous pulley, 72 synchronous belt, 81 drive motor, 82 spline shaft, 83 first drive bevel gear, 84 second drive bevel gear, 85 transmission bevel gear. Detailed Implementation

[0031] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0032] Please see Figure 1-10The flanging mechanism for the sewing machine includes a connecting bracket 1, a movable bracket 2, a main assembly frame 31, and a secondary assembly frame 32. The main assembly frame 31 is fixedly installed in the connecting bracket 1. The movable bracket 2 includes two sets that are slidably installed in the connecting bracket 1, and a support spring 21 is installed between the movable bracket 2 and the connecting bracket 1. Each set of movable brackets 2 is fixedly installed with a secondary assembly frame 32. The main assembly frame 31 and the secondary assembly frame 32 are arranged in a relative manner.

[0033] It also includes a first folding wheel 41, a second folding wheel 42, a first flanging wheel 51, a second flanging wheel 52, and a transfer roller 6. The first folding wheel 41 and the second folding wheel 42 are arranged in a relatively opposite manner and are rotatably mounted on the main assembly frame 31 and one of the auxiliary assembly frames 32, respectively. The first flanging wheel 51 and the second flanging wheel 52 are rotatably mounted on the main assembly frame 31 and are arranged sequentially on the downstream side of the first folding wheel 41. The transfer roller 6 is rotatably mounted on both the main assembly frame 31 and the auxiliary assembly frame 32, and the transfer rollers 6 mounted on the main assembly frame 31 and the auxiliary assembly frame 32 are arranged in a relatively opposite manner.

[0034] The connecting bracket 1 is fixedly installed on the sewing machine in a detachable manner, and the connecting bracket 1 is connected to the packaging bag conveying mechanism on the sewing machine so that the conveying roller 6, each folding and turning roller mounted on its inner side can receive the packaging bag conveyed by the packaging bag conveying mechanism and turn the bag opening into a turn-up. The turned-up packaging bag is then conveyed to the sewing machine for sealing through the conveying roller 6.

[0035] The main assembly frame 31 is fixed to the connecting bracket 1 by bolt assembly 33. The first folding wheel 41, the first flanging wheel 51, and the second flanging wheel 52 are assembled at the center of the main assembly frame 31, and multiple sets of transfer rollers 6 are assembled on both sides of the main assembly frame 31. The axes of the first folding wheel 41, the second folding wheel 42, and the transfer rollers 6 are all arranged in the vertical direction, while the axes of the first flanging wheel 51 and the second flanging wheel 52 are kept in the horizontal direction.

[0036] Both sets of movable brackets 2 are fixedly mounted with auxiliary assembly frames 32 by bolt assemblies 33. The transmission rollers 6 mounted on the auxiliary assembly frames 32 are arranged relative to the transmission rollers 6 on the main assembly frame 31, which can stably transmit the packaging bags between the two sets of transmission rollers 6. The two sets of auxiliary assembly frames 32 are respectively arranged on both sides of the main assembly frame 31.

[0037] The first folding wheel 41 and the second folding wheel 42 are arranged in opposite directions, which can fold the vertical packaging bag opening into an inclined position. After being processed by the first folding wheel 51 and the second folding wheel 52 in sequence, the bag opening is folded down 180°. Then, the sewing machine sews the folded bag opening to ensure the sealing effect of the packaging bag opening.

[0038] The two sets of movable brackets 2 and the auxiliary assembly brackets 32 mounted on them move towards the side closer to the main assembly bracket 31 under the action of the support spring 21, so that the two side transmission rollers 6 are kept in close contact, and the first folding wheel 41 and the second folding wheel 42 are kept in close contact, so as to stably transport the packaging bags.

[0039] To ensure that the movable bracket 2 can be stably assembled on the connecting bracket 1 in a relatively sliding manner, and to ensure that the support spring 21 can stably drive the movable bracket 2 to move closer to the main assembly frame 31, the following technical solution is provided.

[0040] A bearing base plate 11 is fixedly connected to the bottom of the connecting bracket 1. Guide grooves 12 are provided on the top of the connecting bracket 1 and the bearing base plate 11. Guide seats 22 are fixedly connected to the upper and lower sides of the movable bracket 2. The guide seats 22 and the guide grooves 12 are in a sliding combination. A guide post 23 is fixedly connected to the outer side of the movable bracket 2 and is in a sliding insertion with the side wall of the connecting bracket 1. A support spring 21 is wrapped around the guide post 23, and the two ends of the support spring 21 are respectively in contact with the movable bracket 2 and the connecting bracket 1.

[0041] The matching combination of guide groove 12, guide seat 22 and guide column 23 can ensure that the movable bracket 2 slides stably in the horizontal direction in the connecting bracket 1, while the elastic force provided by the support spring 21 can drive the movable bracket 2 to move closer to the main assembly frame 31, so that the transmission roller 6 on the auxiliary assembly frame 32 and the transmission roller 6 on the main assembly frame can be aligned to effectively clamp the packaging bag between them and ensure its stable transmission.

[0042] At the same time, it can also cause the second folding wheel 42 mounted on the sub-assembly frame 32 to rotate towards the first folding wheel 41. The two work together to effectively fold the opening of the passing packaging bag.

[0043] To ensure that each folding and turning wheel can effectively fold and turn the edges of the bag opening, the following technical solution is provided.

[0044] The top outer edge of the first folding wheel 41 is provided with an annular protrusion 411, and the top outer edge of the second folding wheel 42 is provided with an annular recess 421 that matches the annular protrusion 411. The outer edges of the first folding wheel 51 and the second folding wheel 52 are both provided with folding annular grooves 53.

[0045] The annular protrusion 411 on the first folding wheel 41 works in conjunction with the annular recess 421 on the second folding wheel 42 to fold the originally vertical bag opening toward the sub-assembly frame 32 into an inclined posture. The inclination angle of the folding ring groove 53 on the first folding wheel 51 is smaller than that on the second folding wheel 52. When the bag opening in the inclined posture passes through the two sets of folding ring grooves 53 in sequence, the bag opening can be folded 180°.

[0046] To ensure that the first folding wheel 41 and the transfer roller 6 mounted on the main assembly frame 31 operate synchronously, to ensure that the second folding wheel 42 and the transfer roller 6 mounted on one set of auxiliary assembly frames 32 operate synchronously, and to ensure that the transfer roller 6 mounted on another set of auxiliary assembly frames 32 operates synchronously, the following technical solutions are provided.

[0047] Synchronous pulleys 71 are fixed to the same end of the first folding wheel 41, the second folding wheel 42, and each set of transmission rollers 6. The synchronous pulleys 71 mounted on the main assembly frame 31 are powered by synchronous belts 72. The synchronous pulleys 71 on the two sets of auxiliary assembly frames 32 are powered by two sets of synchronous belts 72 respectively.

[0048] According to the above assembly scheme, it can be ensured that each set of transmission rollers 6 and the first folding wheel 41 on the main assembly frame 31 operate synchronously, and that the transmission rollers 6 and the second folding wheel 42 on the two sets of auxiliary assembly frames 32 operate synchronously.

[0049] Setting the movable support 2 and the auxiliary assembly frame 32 as two independent sets ensures that the conveying rollers 6 and the second folding roller 42 on them can stably clamp and convey the packaging bag. When conveying the packaging bag, the distance between the two conveying rollers 6 on the upstream auxiliary assembly frame 32 and its conveying rollers 6 is the thickness of two layers of bag wall. When the packaging bag is conveyed to the downstream side after being processed by each folding roller and folding roller, the distance between the two conveying rollers 6 on both sides is the thickness of four layers of bag wall. By independently adjusting the two sets of movable supports 2 and auxiliary assembly frames 32, it can be ensured that the packaging bag can be clamped and conveyed stably at each position.

[0050] To ensure that the transfer rollers 6 and No. 1 folding roller 41 on the main assembly frame 31 and the transfer rollers 6 and No. 2 folding roller 42 on the auxiliary assembly frame 32 maintain opposite and equal speed operation, the following technical solution is provided.

[0051] It also includes a drive motor 81, a splined shaft 82, a first drive bevel gear 83, a second drive bevel gear 84, and a transmission bevel gear 85. The drive motor 81 is fixedly mounted on the connecting bracket 1. The splined shaft 82 includes two sets arranged side by side. The two sets of splined shafts 82 are rotatably mounted on the connecting bracket 1 and the main assembly frame 31 and are arranged through the movable bracket 2. One set of splined shafts 82 is powered by the drive motor 81. A first drive bevel gear 83 is fixedly connected to both sets of splined shafts 82. A second drive bevel gear 84 is rotatably mounted on both sets of auxiliary assembly frames 32. The two sets of second drive bevel gears 84 are slidably inserted into the two sets of sliding shafts respectively. A transmission bevel gear 85 is mounted on some of the transmission rollers 6. The transmission bevel gear 85 is meshed with the first drive bevel gear 83 or the second drive bevel gear 84 at the corresponding position.

[0052] Specifically, transmission bevel gears 85 are fixedly connected to the transmission rollers 6 at both ends of the main assembly frame 31. These two sets of transmission bevel gears 85 mesh with two sets of first-stage drive bevel gears 83, respectively. Similarly, transmission bevel gears 85 are fixedly connected to the transmission rollers 6 at corresponding positions on the two sets of main assembly frames 31, and these two sets of transmission bevel gears 85 mesh with two sets of second-stage drive bevel gears 84, respectively. The first-stage drive bevel gears 83 and second-stage drive bevel gears 84, arranged on the same splined shaft 82, are symmetrically arranged to ensure that the synchronous pulleys 71 on the main assembly frame 31 and the auxiliary assembly frame 32 maintain constant speed and reverse rotation.

[0053] The second drive bevel gear 84 and the spline shaft 82 are slidably connected, which ensures that when the sub-assembly frame 32 is driven horizontally by the support spring 21, the corresponding second drive bevel gear 84 always maintains a power combination with the spline shaft 82, and the power of the spline shaft 82 can be stably transmitted to the second drive bevel gear 84.

[0054] When the drive motor 81 is working, it drives the sliding key shaft directly connected to it to rotate, which in turn drives the first drive bevel gear 83 and the second drive bevel gear 84 on it to rotate stably, and then transmits power to the corresponding transmission bevel gear 85. Through the combination of synchronous pulley 71 and synchronous belt 72, it can drive the synchronous pulleys 71 on the main assembly frame 31 and the corresponding auxiliary assembly frame 32 to rotate stably, thereby realizing the stable operation of the transmission roller 6, the first folding wheel 41 and the second folding wheel 42 on them.

[0055] For another set of splined shafts 82, the transmission bevel gear 85 mounted on the main mounting frame 31 can drive the first drive bevel gear 83, which meshes with and is mounted on the set of splined shafts 82, to operate stably. In turn, the corresponding second drive bevel gear 84 is driven to operate stably through the set of sliding key shafts, thereby transmitting the data to the sets of transmission rollers 6 on the corresponding auxiliary mounting frame 32 of the second drive bevel gear 84.

[0056] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A flanging mechanism for use with a bag sewing machine, characterized in that: The system includes a connecting bracket (1), a movable bracket (2), a main assembly frame (31), and a secondary assembly frame (32). The main assembly frame (31) is fixedly installed in the connecting bracket (1). The movable bracket (2) includes two sets that are slidably installed in the connecting bracket (1), and a support spring (21) is installed between the movable bracket (2) and the connecting bracket (1). Each set of movable brackets (2) is fixedly installed with a secondary assembly frame (32). The main assembly frame (31) and the secondary assembly frame (32) are arranged relative to each other. The system also includes a first folding wheel (41), a second folding wheel (42), and a first flanging wheel (51). The second flanging wheel (52) and the transfer roller (6) are arranged in a relatively opposite manner and are rotatably mounted on the main assembly frame (31) and one of the sub-assembly frames (32). The first flanging wheel (51) and the second flanging wheel (52) are rotatably mounted on the main assembly frame (31) and are arranged sequentially on the downstream side of the first flanging wheel (41). The transfer roller (6) is rotatably mounted on both the main assembly frame (31) and the sub-assembly frame (32), and the transfer roller (6) mounted on the main assembly frame (31) and the sub-assembly frame (32) are arranged in a relatively opposite manner.

2. The flanging mechanism for a bag sewing machine according to claim 1, characterized in that: The bottom of the connecting bracket (1) is fixedly connected to a bearing base plate (11). The top of the connecting bracket (1) and the bearing base plate (11) are both provided with guide grooves (12). The upper and lower sides of the movable bracket (2) are fixedly connected to guide seats (22). The guide seats (22) and the guide grooves (12) are in a sliding combination. The outer side of the movable bracket (2) is fixedly connected to a guide post (23) that is in a sliding insertion with the side wall of the connecting bracket (1). The support spring (21) is wrapped around the guide post (23), and the two ends of the support spring (21) are respectively in contact with the movable bracket (2) and the connecting bracket (1).

3. The flanging mechanism for a bag sewing machine according to claim 1, characterized in that: The first folding wheel (41) has an annular protrusion (411) on its top outer edge, and the second folding wheel (42) has an annular recess (421) on its top outer edge that matches the annular protrusion (411). The outer edges of the first folding wheel (51) and the second folding wheel (52) are both provided with folding annular grooves (53).

4. The flanging mechanism for a bag sewing machine according to claim 1, characterized in that: The first folding wheel (41), the second folding wheel (42), and each set of transmission rollers (6) are all fixed to the same end with a synchronous wheel (71). Each set of synchronous wheels (71) assembled on the main assembly frame (31) is powered by a synchronous belt (72). The synchronous wheels (71) on the two sets of auxiliary assembly frames (32) are powered by two sets of synchronous belts (72).

5. The flanging mechanism for a bag sewing machine according to claim 4, characterized in that: It also includes a drive motor (81), a splined shaft (82), a first drive bevel gear (83), a second drive bevel gear (84), and a transmission bevel gear (85). The drive motor (81) is fixedly mounted on the connecting bracket (1). The splined shaft (82) includes two sets arranged side by side. The two sets of splined shafts (82) are rotatably mounted on the connecting bracket (1) and the main assembly frame (31) and are arranged through the movable bracket (2). One set of splined shafts (82) has the drive motor (81) 81) Power connection: A first drive bevel gear (83) is fixedly connected to each of the two sets of splined shafts (82), and a second drive bevel gear (84) is rotatably mounted on each of the two sets of auxiliary assembly frames (32). The two sets of second drive bevel gears (84) are slidably inserted into the two sets of sliding shafts respectively. The transmission bevel gear (85) is mounted on some of the transmission rollers (6), and the transmission bevel gear (85) is engaged with the first drive bevel gear (83) or the second drive bevel gear (84) at the corresponding position.

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