A roll-forming device for nonwoven fabric production

Abstract

This utility model provides a roll-forming device for nonwoven fabric production, including a base, two movable seats symmetrically arranged on the base, a drive mechanism between the base and the two movable seats, two rotating rollers respectively rotatably arranged on the two movable seats, a limiting plate respectively arranged on the two rotating rollers, a rotation mechanism between the rotating rollers and the movable seats, two support seats symmetrically arranged on the upper end face of the base, two adjusting slide grooves respectively opened on the upper end face of the two support seats, two adjusting slide rods respectively raised and lowered on the two support seats, a support plate between the two adjusting slide rods, a placement groove on the support plate, and a fixing mechanism respectively arranged between the two adjusting slide rods and the two support seats. When the operator loads the material, there is no need to lift the roll and adjust its posture or manually align it, which can reduce the intensity of the lifting and prevent the roll from slipping or rolling due to physical exhaustion or operational errors, thus avoiding a direct threat to the personal safety of the operator.

Description

Technical Field

[0001] This utility model relates to the field of nonwoven fabric production technology, specifically to a roll-forming device for nonwoven fabric production. Background Technology

[0002] Nonwoven fabric, also known as non-woven textile, is a new type of fiber product formed by directly bonding fiber webs through mechanical, thermal, or chemical methods. It features a short production process, low cost, and wide range of applications, making it a key basic material for many industries such as medical protection, hygiene materials, geotechnical engineering, filtration and sound insulation, and agricultural covering.

[0003] On a continuous production line for nonwoven fabrics, regardless of whether it's spinning, carding, or undergoing reinforcement processes such as hydroentangling, hot rolling, or needle punching, the final step is to wind the continuous sheet of nonwoven fabric into a roll with a certain diameter and density. This process is called "winding" or "rewinding." The purpose of winding is threefold: first, to facilitate subsequent storage, transportation, and logistics management; second, to provide a standardized raw material supply for downstream secondary processing steps such as slitting, printing, and laminating; and third, to maintain stable tension and a smooth roll surface, which is crucial for ensuring the quality of the final product.

[0004] Traditional nonwoven fabric winding devices generally employ a basic architecture of double-sided clamping drive. The core workflow is as follows: the operator first moves the roll (or empty roll) carrying the nonwoven fabric between two movable clamping seats. These two clamping seats are typically driven by a double-ended screw and can move synchronously towards or away from each other. Each clamping seat is equipped with a motor-driven rotating roller and a stop plate (or limit plate) for axial positioning. During operation, the operator manually or with the aid of simple tools lifts one end of the heavy roll (or roll) and aligns it with one of the rotating rollers, simultaneously or slightly lifting the other end. While keeping the roll horizontally suspended, the operator visually and by hand aligns its axis roughly with the theoretical center line of the two clamping seats. Then, the drive is activated, causing the two clamping seats, along with the rotating roller, to move towards each other until the rotating roller supports the roll from both sides and applies sufficient clamping force, while the stop plate adheres to the end face of the roll to complete axial fixation. Finally, the rotating roller is driven to rotate, and the nonwoven fabric is wound.

[0005] However, the traditional operating mode has the following technical defects: during the feeding, centering and initial clamping of the drum, it relies entirely on the operator's arm strength to support and adjust the drum's posture, and manual alignment is required every time the drum is fed. This not only results in extremely high labor intensity, but also makes it very easy for the drum to slip or roll due to physical exhaustion or operational errors, posing a direct threat to the operator's personal safety. Utility Model Content

[0006] The purpose of this invention is to address the shortcomings and deficiencies of the existing technology by providing a roll-forming device for nonwoven fabric production.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a nonwoven fabric production roll forming device, comprising a base, two movable seats symmetrically arranged on the base, a driving mechanism disposed between the base and the two movable seats for driving the two movable seats to move closer or further apart, two rotating rollers respectively rotatably arranged on the two movable seats, limiting discs respectively arranged on the two rotating rollers, a rotating mechanism disposed between the rotating rollers and the movable seats, and further comprising two support seats symmetrically arranged on the upper end face of the base, two adjusting grooves respectively opened on the upper end face of the two support seats, two adjusting slide rods respectively raised and lowered on the two support seats and located in the adjusting grooves, a support plate disposed between the two adjusting slide rods for holding the support roll between the two rotating rollers, a placement groove disposed on the support plate for restricting the front and rear movement of the roll when the support plate supports the roll, and a fixing mechanism respectively disposed between the two adjusting slide rods and the two support seats for fixing or releasing the adjusting slide rods from the adjusting grooves.

[0008] A further improvement is that the placement groove is an inverted conical groove or a trapezoidal groove.

[0009] Further effects: The tapered groove can be adapted to provide support for drums of different sizes.

[0010] A further improvement is that the fixing mechanism includes two fixed side holes respectively opened on the side end faces of the two support seats and connected to the adjusting slide groove, corresponding connecting holes respectively opened on the two adjusting slide rods, and fixed insert rods respectively passing through the fixed side holes and the corresponding connecting holes.

[0011] Further effects: In the default state, the two adjusting slide rods are located in the upper part of the adjusting slide groove. At this time, the positions of the corresponding connecting holes and the fixed side holes are aligned. The fixed rod is inserted into the corresponding connecting holes and the fixed side holes, which restricts the lifting and lowering of the adjusting slide rods in the adjusting slide groove. This ensures that when the support plate supports the drum, the central axis of the drum is aligned with the central axis of the rotating roller.

[0012] Further effects: After the drum is fixed by the two limiting discs, the fixing rod is pulled out from the corresponding connection hole and the fixing side hole, causing the adjusting slide rod to fall naturally under its own weight and the weight of the support plate. This moves the support plate away from the drum, preventing it from affecting the winding effect during winding. After the drum is wound up, due to the increased diameter of the wound drum, the two moving seats can be driven away from each other by the drive mechanism, causing the drum to fall onto the support plate under its own weight. The support plate supports the drum, preventing it from falling onto the base plate and getting dirty. The operator can then remove the wound drum from the support plate and pull the support plate to raise the two adjusting slide rods to the default position in the adjusting groove, aligning the corresponding connection hole and the fixing side hole. The fixing rod is then inserted into the corresponding connection hole and the fixing side hole again, and the operator can place the drum to be wound on the support plate again for support. Since the support plate maintains a specific position in the default state each time, the central axis of the drum can be aligned with the central axis of the rotating roller when placing drums of the same size.

[0013] A further improvement is that: compression springs are provided on the two support seats within the adjusting slide grooves, with the upper and lower ends of the compression springs respectively fixed between the lower end of the adjusting slide rod and the support seat; and secondary side holes are provided on the two support seats for corresponding to the corresponding connecting holes after the adjusting slide rod descends.

[0014] Further effects: When a compression spring is installed and the drum is not placed on it, the compression spring does not undergo elastic deformation. In this case, the fixed side hole and the corresponding connection hole remain aligned. Simply insert the fixing rod directly into the corresponding connection hole and the fixed side hole. The compression spring provides support for the adjusting slide rod, eliminating the need for manual lifting of the support base to maintain the alignment. When the support plate needs to be lowered, first remove the fixing rod from the corresponding connection hole and the fixed side hole, then press down the support base to move the adjusting slide rod in the adjusting groove. Lower the slide until the secondary side hole aligns with the corresponding connection hole. Then insert the fixing rod into the secondary side hole and the corresponding connection hole to prevent the adjusting slide rod from being pushed by the spring and rising in the adjusting groove. If it is necessary to raise the support plate again, pull the fixing rod out of the secondary side hole and the corresponding connection hole. At this time, the compression spring releases its elastic potential energy to push the adjusting slide rod and drive the support plate to rise. Since the compression spring is fixed between the lower end of the adjusting slide rod and the support base, it can prevent the adjusting slide rod from slipping longitudinally out of the adjusting groove and keep the adjusting slide rod in the default state in the adjusting groove.

[0015] A further improvement is that an adjustment device for adjusting the distance between the support plate and the two adjustment slide rods is provided between the support plate and the two adjustment slide rods.

[0016] A further improvement is that the adjusting device includes a guide rod and a threaded rod respectively disposed on the upper end face of the two adjusting slide rods, a threaded inner hole opened on the support plate for threaded engagement with the threaded rod, and a guide hole opened on the support plate for clearance engagement with the guide rod. The threaded rod is rotatably disposed on the upper end of the adjusting slide rod, and the guide rod is fixedly disposed on the upper end of the adjusting slide rod.

[0017] Further effects: Since the diameters of fabric rolls of different sizes are not uniform, the support plate can be raised and lowered by controlling the rotation of the threaded rod. The cooperation between the guide rod and the guide hole restricts the rotation of the support plate, thus enabling the support plate to raise and lower. When the threaded rod is not driven by external force, the self-locking function of the threaded rod and the threaded inner hole restricts the raising and lowering of the support plate, thereby fixing the height of the support plate. The height of the support plate can be adjusted according to the different sizes of fabric rolls in this way.

[0018] A further improvement is that the upper end of the adjusting slide rod is provided with a T-shaped groove, and the lower end of the threaded rod is provided with a T-shaped rod. The upper end of the T-shaped rod is fixedly connected to the lower end of the threaded rod, and the lower end of the T-shaped rod is in clearance fit with the T-shaped groove.

[0019] A further improvement is made to the driving mechanism, which includes a driving opening on the base, a double-ended screw rotatably disposed on the base within the driving opening, a driving block disposed at the lower end of each of the two movable seats within the driving opening and threadedly connected to the double-ended screw for driving the two movable seats closer to or further apart when the double-ended screw rotates, and a driving motor whose fixed end is disposed on the side end face of the base and whose output end is connected to the double-ended screw for driving the double-ended screw to rotate. The driving block is clearance-fitted with the driving opening.

[0020] After adopting the above technical solution, the beneficial effects of this utility model are as follows: When it is necessary to feed the drum, firstly, the support plate is raised to a fixed height by adjusting the sliding rod in the adjusting groove, so that the central axis of the placed drum can correspond to the central axis of the rotating roller. Then, the adjusting rod is fixed in the adjusting groove by the fixing mechanism to fix the raising and lowering of the support plate. Then, the drum is placed on the support plate, and the two moving seats are driven to move closer to each other by the driving mechanism until the limiting plate abuts against the two end faces of the drum. Then, the adjusting rod is released from the adjusting groove by the fixing mechanism, so that the support seat descends under its own weight. One of the rotating rollers is controlled to rotate by the rotating mechanism to drive the drum. During the winding process, the support seat being far from the roll does not affect the winding effect. After winding is completed, the two moving seats can be directly controlled to move away from each other through the drive mechanism, so that the wound fabric roll falls onto the support plate. The operator only needs to remove the wound fabric roll, adjust the support plate to rise to a fixed height, and fix it through the fixing mechanism. Then, place the roll on the support plate for support. Repeating this action will ensure that the central axis of the roll is aligned with the central axis of the rotating roller each time. When loading the material, the operator does not need to lift the roll and adjust its posture or manually align it, which can reduce the intensity of the lifting and prevent the roll from slipping or rolling due to physical exhaustion or operational errors, thus posing a direct threat to the personal safety of the operator. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a front sectional view of the present invention; Figure 2 This is a top view of the present invention; Figure 3 This is a side sectional view of the base, support seat, and support plate in this utility model; Figure 4 It corresponds Figure 3 Another state diagram; Figure 5 It corresponds Figure 3 Enlarged view of part A.

[0023] Explanation of reference numerals in the attached drawings: 1. Base; 2. Movable seat; 3. Rotating roller; 4. Limiting plate; 5. Rotating mechanism; 6. Support seat; 7. Adjusting slide groove; 8. Adjusting slide rod; 9. Support plate; 10. Placement slot; 11. Fixed side hole; 12. Corresponding connection hole; 13. Fixed insertion rod; 14. Compression spring; 15. Secondary side hole; 16. Guide rod; 17. Threaded rod; 18. Threaded inner hole; 19. Guide hole; 20. T-slot; 21. T-shaped rod; 22. Drive opening; 23. Double-ended screw; 24. Drive block; 25. Drive motor. Detailed Implementation

[0024] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0025] See Figures 1 to 5 As shown, the technical solution adopted in this specific embodiment is: a roll-forming device for nonwoven fabric production, including a base 1, two movable seats 2 symmetrically arranged on the base 1, a driving mechanism between the base 1 and the two movable seats 2 for driving the two movable seats 2 to move closer or further apart, two rotating rollers 3 respectively rotatably arranged on the two movable seats 2, a limiting plate 4 respectively arranged on the two rotating rollers 3, a rotating mechanism 5 arranged between the rotating rollers 3 and the movable seats 2, and also including two support seats 6 symmetrically arranged on the upper end face of the base 1, two adjusting grooves 7 respectively opened on the upper end face of the two support seats 6, two adjusting slide rods 8 respectively raised and lowered on the two support seats 6 and located in the adjusting grooves 7, a support plate 9 arranged between the two adjusting slide rods 8 for holding the support roll between the two rotating rollers 3, a placement groove 10 arranged on the support plate 9 for restricting the front and rear movement of the roll when the support plate 9 supports the roll, and a fixing mechanism respectively arranged between the two adjusting slide rods 8 and the two support seats 6 for fixing or unfixing the adjusting slide rods 8 in the adjusting grooves 7. The rotating mechanism 5 is a servo motor with its fixed end mounted on one of the movable seats 2 and its output end connected to the corresponding rotating roller 3. Since the drum rests against two limit discs 4, winding the drum can be achieved by controlling one of the rotating rollers 3 to rotate the limit disc 4. The limit disc 4 and the rotating roller 3 are fixedly connected by welding.

[0026] The placement groove 10 is an inverted conical groove or a trapezoidal groove.

[0027] The fixing mechanism includes two fixing side holes 11 respectively opened on the side end faces of the two support seats 6 and connected to the adjusting slide groove 7, corresponding connecting holes 12 respectively opened on the two adjusting slide rods 8, and fixing insert rods 13 respectively passing through the fixing side holes 11 and the corresponding connecting holes 12.

[0028] Compression springs 14 are installed on the two support bases 6 within the adjusting slide grooves 7. The upper and lower ends of the compression springs 14 are fixed between the lower end of the adjusting slide rod 8 and the support base 6, respectively. The two support bases 6 are provided with secondary side holes 15 corresponding to the corresponding connecting holes 12 after the adjusting slide rod 8 is lowered. The secondary side holes 15 are located below the fixed side holes 11 and have the same diameter as the fixed side holes 11.

[0029] An adjustment device is provided between the support plate 9 and the two adjusting slide rods 8 to adjust the distance between the support plate 9 and the adjusting slide rods 8.

[0030] The adjusting device includes a guide rod 16 and a threaded rod 17 respectively disposed on the upper end face of the two adjusting slide rods 8, a threaded inner hole 18 opened on the support plate 9 for threaded engagement with the threaded rod 17, and a guide hole 19 opened on the support plate 9 for clearance engagement with the guide rod 16. The threaded rod 17 is rotatably disposed on the upper end of the adjusting slide rod 8, and the guide rod 16 is fixedly disposed on the upper end of the adjusting slide rod 8.

[0031] The upper end of the adjusting slide rod 8 has a T-slot 20, and the lower end of the threaded rod 17 has a T-shaped rod 21. The upper end of the T-shaped rod 21 is fixedly connected to the lower end of the threaded rod 17, and the lower end of the T-shaped rod 21 is clearance-fitted with the T-slot 20. The guide rod 16 is fixed to the upper end face of one of the adjusting slide rods 8 by welding or bonding. The threaded rod 17 is rotatably mounted on the upper end of the other adjusting slide rod 8. The adjusting slide rod 8 is assembled in separate parts to allow the T-shaped rod 21 to be inserted into the T-slot 20. It is assembled by splicing and welding. After assembly, the T-shaped rod 21 and the T-slot 20 limit the lifting and lowering of the threaded rod 17 and realize the rotation control of the threaded rod 17 on the adjusting slide rod 8.

[0032] The drive mechanism includes a drive opening 22 on the base 1, a double-ended screw 23 rotatably mounted on the base 1 within the drive opening 22, drive blocks 24 located at the lower ends of two movable seats 2 within the drive opening 22 and threadedly connected to the double-ended screw 23 for moving the two movable seats 2 closer together or further apart when the double-ended screw 23 rotates, and a drive motor 25 fixed at the side end face of the base 1 and connected to the output end of the double-ended screw 23 for driving the double-ended screw 23 to rotate. The drive blocks 24 are clearance-fitted with the drive opening 22. The drive motor 25 is a servo motor. Both ends of the double-ended screw 23 are mounted on the base 1 via bearings, and the output end of the drive motor 25 is connected to one end of the double-ended screw 23 via a coupling. The double-ended screw 23 consists of two screws with oppositely oriented threaded surfaces, used to control the two drive blocks 24 to move closer together or further apart during rotation.

[0033] The working principle of this utility model is as follows: When feeding the drum, the support plate 9 is raised to a fixed height (the position of the fixed side hole 11 corresponds to the position of the corresponding connecting hole 12) by adjusting the sliding rod 8 in the adjusting groove 7. This ensures that the central axis of the placed drum corresponds to the central axis of the rotating roller 3. Then, the fixing rod 13 is inserted into the corresponding connecting hole 12 and the fixing side hole 11, thereby fixing the adjusting rod 8 in the adjusting groove 7 to fix the raising and lowering of the support plate 9. The drum is then placed on the support plate 9, and the double-headed screw 23 is driven to rotate by the drive motor 25, causing the two drive blocks 24 to drive the two moving seats 2 to move closer to each other until the limit plate 4 abuts against the two end faces of the drum. Then, the fixing rod 13 is pulled out from the corresponding connecting hole 12 and the fixing side hole 11, allowing the adjusting rod 8 to naturally descend under its own weight and the weight of the support plate 9. The rotating mechanism 5 controls one of the rotating rollers 3. The rotation drives the roll to perform the winding process. During winding, the support seat 6 is far away from the roll and will not affect the winding effect. After winding, the two moving seats 2 can be directly controlled to move away from each other through the drive mechanism, so that the wound cloth roll falls onto the support plate 9, preventing the roll from falling onto the bottom plate and getting dirty. The operator only needs to remove the wound cloth roll, and then pull the support plate 9 to drive the two adjusting slide rods 8 to rise to the default state in the adjusting slide groove 7 (the fixed side hole 11 and the corresponding connecting hole 12 are aligned), and fix it through the fixed insertion rod 13. Then place the roll on the support plate 9 for support. Repeat this action so that the central axis of the roll is aligned with the central axis of the rotating roller 3 each time. When the operator loads the material, there is no need to lift the roll and adjust its posture or manually align it. This can reduce the lifting intensity and prevent the roll from slipping or rolling due to physical exhaustion or operation errors, which poses a direct threat to the personal safety of the operator. When the compression spring 14 is installed and the drum is not placed on it, the compression spring 14 does not undergo elastic deformation. At this time, the fixed side hole 11 and the corresponding connecting hole 12 remain aligned. Simply insert the fixing rod 13 directly into the corresponding connecting hole 12 and the fixed side hole 11. The compression spring 14 provides support for the adjusting slide rod 8, eliminating the need for manual continuous lifting of the support base 6 to maintain the alignment of the fixed side hole 11 and the corresponding connecting hole 12. When it is necessary to lower the support plate 9, first remove the fixing rod 13 from the corresponding connecting hole 12 and the fixed side hole 11, then press down the support base 6 to drive the adjusting slide rod 8 down in the adjusting groove 7. When the positions of the secondary side hole 15 and the corresponding connecting hole 12 are aligned, the fixing rod 13 is inserted into the secondary side hole 15 and the corresponding connecting hole 12 to prevent the adjusting slide rod 8 from being pushed by the spring and rising in the adjusting slide groove 7. If it is necessary to raise the support plate 9 again, the fixing rod 13 is pulled out from the secondary side hole 15 and the corresponding connecting hole 12. At this time, the compression spring 14 releases elastic potential energy to push the adjusting slide rod 8 and drive the support plate 9 to rise. Since the compression spring 14 is fixed between the lower end of the adjusting slide rod 8 and the support seat 6, it can prevent the adjusting slide rod 8 from sliding longitudinally out of the adjusting slide groove 7 and keep the adjusting slide rod 8 in the adjusting slide groove 7 in the default state. Since the diameters of fabric rolls of different sizes are not uniform, the support plate 9 can be raised and lowered by controlling the rotation of the threaded rod 17. The cooperation between the guide rod 16 and the guide hole 19 restricts the rotation of the support plate 9, thereby enabling the support plate 9 to raise and lower. When the threaded rod 17 is not driven by external force, the self-locking function of the threaded rod 17 and the threaded inner hole 18 restricts the raising and lowering of the support plate 9, thereby fixing the height of the support plate 9. The height of the support plate 9 can be adjusted according to the different sizes of fabric rolls in this way.

[0034] This utility model aims to protect the structure of the product. The model numbers of the individual components are not the subject of this utility model's protection and are already known technology. Any component on the market that can achieve the functions described above can be selected and applied as a rolling device for nonwoven fabric production. Therefore, the model numbers and other parameters of the components are not described in detail in this utility model. The contribution of this utility model lies in the scientific combination of the various components.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions provided are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection of this utility model as defined by the appended claims and their equivalents. Any aspects of this utility model not detailed herein are well-known to those skilled in the art.

Claims

1. A roll-forming device for nonwoven fabric production, comprising a base, two movable seats symmetrically arranged on the base, a driving mechanism disposed between the base and the two movable seats for driving the two movable seats to move closer or further apart, two rotating rollers respectively rotatably disposed on the two movable seats, limiting disks respectively disposed on the two rotating rollers, and a rotating mechanism disposed between the rotating rollers and the movable seats, characterized in that: It also includes two support seats symmetrically arranged on the upper end face of the base, two adjusting slide grooves respectively opened on the upper end face of the two support seats, two adjusting slide rods respectively raised and lowered on the two support seats and located in the adjusting slide grooves, a support plate arranged between the two adjusting slide rods for holding the support drum between the two rotating rollers, a placement groove arranged on the support plate for restricting the front and rear movement of the drum when the support plate supports the drum, and a fixing mechanism respectively arranged between the two adjusting slide rods and the two support seats for fixing or unfixing the adjusting slide rods in the adjusting slide grooves.

2. The roll forming device for nonwoven fabric production according to claim 1, characterized in that: The placement groove is an inverted conical groove or a trapezoidal groove.

3. The device according to claim 1, wherein: The fixing mechanism includes two fixing side holes respectively opened on the side end faces of the two support seats and connected to the adjusting slide groove, corresponding connecting holes respectively opened on the two adjusting slide rods, and fixing inserts respectively passing through the fixing side holes and the corresponding connecting holes.

4. The device according to claim 3, wherein: Compression springs are installed on the two support seats within the adjusting slide grooves. The upper and lower ends of the compression springs are respectively fixed between the lower end of the adjusting slide rod and the support seat. The two support seats are provided with secondary side holes corresponding to the corresponding connecting holes after the adjusting slide rod descends.

5. The device according to claim 2, wherein: An adjustment device is provided between the support plate and the two adjustment slide rods for adjusting the distance between the support plate and the adjustment slide rods.

6. The device according to claim 5, wherein: The adjusting device includes a guide rod and a threaded rod respectively disposed on the upper end face of the two adjusting slide rods, a threaded inner hole opened on the support plate for threaded engagement with the threaded rod, and a guide hole opened on the support plate for clearance engagement with the guide rod. The threaded rod is rotatably disposed on the upper end of the adjusting slide rod, and the guide rod is fixedly disposed on the upper end of the adjusting slide rod.

7. A roll-forming device for nonwoven fabric production according to claim 6, characterized in that: The upper end of the adjusting slide rod is provided with a T-shaped groove, and the lower end of the threaded rod is provided with a T-shaped rod. The upper end of the T-shaped rod is fixedly connected to the lower end of the threaded rod, and the lower end of the T-shaped rod is in clearance fit with the T-shaped groove.

8. The roll-up device for nonwoven fabric production according to claim 1, characterized in that: The driving mechanism includes a driving opening on the base, a double-ended screw rotatably disposed on the base within the driving opening, a driving block disposed at the lower end of each of the two movable seats within the driving opening and threadedly connected to the double-ended screw for driving the two movable seats closer to or further apart when the double-ended screw rotates, and a driving motor fixed at the side end face of the base and connected to the double-ended screw for driving the double-ended screw to rotate. The driving block is clearance-fitted with the driving opening.

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